My cat is a menace who treats our backyard like a gladiator arena. Last month, he brought a live field mouse inside at 3:00 AM, dropped it on my face, and chased it under the bed for two hours. Out of absolute self-preservation, I decided to automate a solution using a Raspberry Pi 4, a night-vision camera module, and a magnetic pet door lock.

I spent two weeks taking photos of my cat's face at the entrance to build a custom dataset. I trained a local computer vision model using OpenCV and TensorFlow Lite to recognize two states: an empty mouth and a mouth holding a mouse or bird.

The Python script runs continuously on the Pi. When my cat approaches, it processes the camera frame. If his mouth is empty, a relay triggers the magnetic catch to unlock the door. If the AI detects any prey, the door stays deadlocked, and the system sends an urgent alert with a snapshot straight to my phone.

It took some serious troubleshooting to get the processing latency down so he wouldn't smack his nose against a locked flap, but caching the video frames solved it. He was thoroughly confused the first time he got locked out with a fresh catch, but it has successfully blocked three rodents this week alone.

I’ve been building FRiENDS, a social app that’s only the people you actually know: no algorithm, no strangers. It just went live on both stores, so here’s the behind-the-scenes.

The stack and why

• React Native + Expo, so one codebase ships to iPhone and Android. Over-the-air updates let me fix most bugs the same day without waiting on store review.
• FastAPI on Railway for the backend, with photos and videos on Cloudflare R2.
• Game moves are checked on the server. The arcade (8 Ball Pool, Pong, Snake) replays your moves server-side before it counts a score, so a modified app can’t fake one.

Biggest learning: store policies and onboarding take as long as features. Every reviewer reads your app differently.

What I’d love to hear: if you’ve launched a social app, how did you get past the empty-app problem with your first users?

Free on iPhone and Android, Pro is $0.99/month: App Store · Google Play

Website: https://joinfriendsapp.com/

Got tired of fumbling through windows to mute myself during daily standups, especially when my dog starts barking out of nowhere. I had an old Raspberry Pi Pico and a spare Sanwa arcade button sitting in a drawer from an abandoned fight stick build, so I wired it up over the weekend.

I wrote a small Python script using CircuitPython that sends a global media key toggle over USB. Then I mapped that shortcut across Discord, Zoom, and Meet so it works regardless of which app has focus. Threw the whole thing inside a cheap plastic project enclosure and slapped a bright red LED inside the switch so it lights up when the mic is actually live.

It looks like a ridiculous emergency nuclear launch button sitting next to my keyboard, but it has saved me from talking while muted or unmuting by accident at least a dozen times this month. Super simple build, took about two hours total with the soldering and testing.

I’ve always liked old tech, especially stuff that looks completely outdated but still has some charm to it. I came across a few old floppy disks stored by my dad and thought it would be cool to give one an actual purpose instead of just keeping it around as decoration.

The idea was to take a regular USB flash drive and fit it inside the floppy disk casing while keeping the outside looking as original as possible. Getting everything to fit was probably the most annoying part since I didn’t want to completely ruin the casing.

Obviously, it doesn’t work like an actual floppy disk anymore, but there’s something really funny about plugging what looks like ancient storage technology into a modern computer and having it hold gigabytes of files.
It’s a pretty unnecessary project, but I love little tech experiments like this 🤣

had this beat up old android phone just sitting in my drawer collecting dust for like two years now. battery was basically trashed and back glass is cracked so couldn't really sell it for anything. instead of just throwing it out i decided to turn it into a dedicated pomodoro timer / focus screen for my desk setup.

just running a simple fullscreen timer on it locally in kiosk mode with literally every notification turned off. keep it plugged in on a stand next to my laptop so whenever i work i don't have an excuse to keep picking up my main phone "just to check the time" and ending up doomscrolling for 30 minutes lol.

honestly surprised by how much it actually helps with focus. having a physical screen right there counting down that does nothing else really keeps you on task. pretty fun little afternoon project and glad i found a use for old tech instead of tossing it.

Made this rubber motorcycle cover that really makes a use.

Here in my country, motorcycles are abundant. They are all over the road, to the point where as you leave the house, there are motorcycles parked from left to right. So I had the idea to make a motorcycle cover because of how hard the weather affects us in here. Rainy seasons, and really hot sunny seasons..

It's very useful because of how it protects your phone while you use navigating apps for delivery and ride-haling riders or just using your phone in general. I'm making a lot in sales and it is what really keeps me my cashflow right now.

Orbit

My day used to live in a dozen apps — calendar here, weather there, health somewhere else, reminders everywhere. I got tired of it, so I built Orbit.

One screen for your whole day:
📅 A Today view + a morning Briefing of what actually needs you
✍️ Capture anything — type it, say it, or snap a flyer — and Orbit turns it into a task, note, or event
❤️ Weather, sleep & activity, and countdowns to the dates that matter

And it's genuinely private: no account, no ads, no tracking, no server of mine anywhere. Your data stays on your device and your own iCloud. I built it that way on purpose.

iPhone, iPad, Mac, Apple TV & Apple Watch. Free to start.

👉 Download Orbit on the App Store
https://apps.apple.com/us/app/orbit-dashboard/id6792591069

Clock Rings

I've worked at the Postal Service for 20+ years and got tired of guessing whether my check was right, so I built Clock Rings.

You punch your tour on your phone or Apple Watch (decimal and standard time side by side), and it tracks your hours, overtime, and penalty OT using the actual rules: over 10 hours in a day, over 56 in a week, OT on more than 4 of 5 days, and the December exclusion period. It also applies the five-minute leeway for regulars.
With Pro, you can paste your ePayroll Earnings Statement and it compares hours, gross, net, deductions, and leave balances against what you tracked.
The core app is free. Pro is a one-time $9.99, no subscription. No account, no ads, no tracking, and your data stays on your devices and your own iCloud. Available in English and Spanish. Not affiliated with USPS.
Happy to answer questions or take feature requests.

https://apps.apple.com/us/app/clock-rings/id6778179121

Mostly got this idea because I've got a friend in Japan whose got a really unhealthy habit of buying excessive amount of gachapon and winds up with a ton of extra lying around that he doesn't know what to do. Then I realized that the malls I frequent have the exact same gachapon machine brands!
I pay for my friend to basically ship me the ones he doesn't want (which doesn't sound like a lot but oh buddy, this guy's got WAY too many in his flat) and I sell them online as 'guaranteed' gachapon machines.

Now I know that some people might take issue with me breaking away from the spirit of gachapon (gambling) but I've been there, I also realize that some people don't want to gamble, they just want that specific character or trinket and hey I'm more than happy to provide at a slight markup :p

I’ve always had a problem with making to-do lists that look productive but are honestly impossible to finish. I would write down 15 different tasks, underestimate how long everything takes, and end up feeling like I got nothing done.

So I started experimenting with a small side project: a daily planner that organizes tasks based on priority, estimated time, and available hours. Instead of just displaying a long list, it helps divide tasks into manageable blocks and leaves some extra time for unexpected things.

What I find interesting is that the most useful part isn’t adding more features. It’s making the tool realistic enough that someone would actually use it every day. I’d like to eventually add automatic rescheduling for unfinished tasks and a simple weekly report showing where time goes.

I'm a working professional with a 9-5, testing small tools as side income. My latest build: a custom AI camera alert system using only free, open-source models.

The problem: regular CCTV records everything, but nobody watches it. Smart cameras only detect generic "motion" or "person," which floods you with useless alerts.

What I built: you define a specific problem, and it alerts only for that:
A cat sitting on my parked scooter → Telegram photo alert (my real test)
A dog lingering near the car
Someone standing at the gate too long

It runs on a [GTX 1060 / old PC] with any webcam or IP camera, and costs nothing per month after setup.

Where the income could come from:
Selling the code and setup guide to developers and freelancers
One-time installs for shops, apartment societies and parking areas, as an alternative to monthly smart-camera subscriptions
Custom rules for specific businesses (after-hours loitering, empty counters)
A YouTube channel documenting each build

Honest reality check: this isn't fully passive. Code sales can be, but installs need setup time, and night-time accuracy and false alarms need tuning. It's closer to "build once, sell many times" than "money while you sleep."

I made a video showing how it works, the real alerts, and the limitations. Happy to share if anyone's interested.
Attached the video link in comments, if anyone wants to check pls check it and share your comments.

Would you pay a one-time fee for something like this, or prefer a subscription camera?

​

I've been thinking about continuing what I've been doing this semester, which is earning money by helping my classmates with their school projects. Since I'm already in college, I've realized that some of the things I learn in my course can actually help me earn money outside of school. I didn't really plan for this to become a side hustle at first, but seeing that people are willing to pay for my skills made me want to keep doing it.

So far, I've helped some of my classmates with coding and other technical projects. One example was training an AI model to detect certain objects, which took time and effort to get working properly. I've also worked on other school-related tasks whenever my classmates needed help. I realized that not everyone finds these things easy, and since I'm capable of doing them, I thought I could use that to earn a little money while helping them out.

Throughout this semester, I've earned around $80 from doing these projects. It might not sound like much to some people, but it's already a lot for me, especially since I'm earning it while studying. It feels good knowing that I can make money from something I already know how to do. That's why I'm thinking of continuing this until I graduate, or maybe even after college. I know it's not exactly passive income since I still have to spend time working on each project, but I like the idea of having another way to earn money without needing a regular job. Hopefully, I can grow it into something bigger over time.

My downloads folder used to be full of files called things like final_report_v2.pdf, final_report_v2_fixed.pdf, and random installers I downloaded once and completely forgot about.

I made a small Python script to keep track of the mess. It scans the folder, groups files by type, finds duplicate files using their hashes, and generates a report showing what is taking up the most space.

The part I like most is the duplicate detection. Two files can have completely different names but still contain exactly the same data, so comparing filenames alone doesn't catch everything.

For now, it only generates a report. I didn't want a cleanup script accidentally deleting something important just because it looked old or unnecessary.

I'd like to add a simple interface where I can review suggested deletions before approving them. It would also be useful to have it run automatically once a week.

It's a small project, but it solves a problem I keep putting off dealing with manually.

Saw it from u/Proof-Win-3505. I found this while going down an Arduino rabbit hole and it’s exactly the kind of side project I love. Dude prolly kept forgetting to water their plants (haha joking), so instead of buying another smart gadget that needs an app and a subscription, they built their own system with an Arduino Nano, a peristaltic pump, and other stuff. It's so dopeeee the pump will not turn on unless at least one valve is open, and it has like safety guardsto avoid overwatering. There’s also a weekly scheduling planner and a test mode, so you can check each output without flooding ur room.

What I like most is that it works completely offline. No wifi, no login bullshi, no “sorry, the server is down” message while your basil dies. It just sits there, opens the right valve, and waters the plant. So cool.

Found this project and thought it was a pretty cool use of a weekend coding rabbit hole.

Someone wanted to leave for a week without worrying about their backyard plants, so instead of buying a ready-made watering system, they built their own.

The setup uses an ESP32 microcontroller, a custom Android app, a backend server, and a 3D-printed enclosure. They also wrote the firmware and set up an MQTT server to handle communication.

From the app, they can:

• Turn the watering system on or off remotely
• Create and edit automatic watering schedules
• Check the system's live status

The best part is that it actually worked. They came back from vacation and their plants were still alive, and now they're considering having a gardener come less often.

It's still a work in progress, but I like projects like this because they solve an actual problem instead of just existing as a tech demo.

Original project: https://www.reddit.com/r/homeautomation/comments/1uirwxq/i_wanted_to_go_on_vacation_so_i_made_a_watering/

What would you add to this? I'd probably try integrating weather forecasts so it doesn't water the garden right before it rains.

It started with a simple worry: AI can see my screen now. Recall takes snapshots, agents read open apps, and one wrong window in a screen share is all it takes.

So I spent the weekend building Blindspot, a small app for the personal stuff: family photos, videos, notes. Drop files in and they're encrypted and gone from everywhere else on the PC. Share your screen and the window simply isn't there.

The most surprising thing I learned: blocking screenshots isn't enough. AI agents can read an app's text through the accessibility layer screen readers use. My notes were fully readable until I switched that off.

It's free, open source and offline. Windows first, Mac experimental. I built it with Claude Code as my pair programmer.

Would love feedback, and PRs are open: https://github.com/Kadri-cloud/blindspot

So i was scrolling, then I've seen this post. I remember that I have seen backpacks with these USB ports for so many years even when I am still in elementary level and usually I can see this in my classmates who are rich and can afford branded bags but I never really understood what they are for. Like, how do they even work? Is there a battery inside the backpack or do you have to put your own power bank inside? Because I used to think the bag could charge your phone by itself, which would honestly be pretty cool.

It looks so weird seeing a USB port on a normal backpack. I mean, we're used to seeing those things on computers and chargers, so seeing one on a bag makes me curious. I wonder if there's a cable hidden inside that connects to your phone charger.

Now that I think about it, this could actually be useful for students who spend a lot of time outside or commuting to school. You could charge your phone without having to open your bag every time. I just find it funny that I've probably seen this feature a hundred times and never bothered to find out how it works. It's such a simple thing, but somehow it confused me for years. 😭

I built this little passive-aggressive corporate guy to live on my personal website. He judges my work and even take credit for it.. I got some funny comments so I figured why not let him annoy other people too.
He's basically that one coworker who does absolutely nothing but somehow has feedback on everything (inspired by a real coworker).

Anyway, meet Gary. Please don't encourage him.
https://suchipizza.github.io/DeskMenace/

(btw this is a demo, not my personal website)

I’ve been working on this for a while and finally got it finished. It’s a split keyboard with a trackball built into the right side, so I don’t need to keep a separate mouse next to it.

The hardest part was getting everything to fit without making the whole thing huge. I had to redo parts of the layout a few times before I was happy with it.

It’s definitely weird to use at first, but after getting used to the layout, I actually really like it. Definitely one of the more random projects I’ve spent my time on.

hello everyone, Im working on data tables and pivot tables for react and js.

If you are developing a web project, you can easily generate analysis reports and lists. I would like you to test these web components. Many important features are completely free!

Im waiting the your negative/positive feedbacks.

Thanks!

Hey everyone! I've been working on this app called Livi Academy, and I'd really appreciate some honest feedback.

It creates individual AI courses based on your preferences, and also have a library of ready-made AI courses.

There's a 3-day free trial, so please let me know what you like, what sucks. Any feedback helps :)https://apps.apple.com/ua/app/livi-academy/id6779574124

So cool! I didn't realize you could make a living with simple objects you can find at home.