Ask HN: Most interesting tech you built for just yourself?

I have a rail line right under my apartment, so I built a small computer vision app running on a Rasperry Pi which records each train passing, and tries to stitch an image of it.

It has a frontend at https://trains.jo-m.ch/.

Edit: it's currently raining and the rain drops are disturbing the images a bit.

This is such a cool project! I live right next to a busy road and for a long time have wanted to do something like this that would count the vehicles passing. I've always been curious how many cars pass on a given day and I feel like the hardest part now adays would be getting the right camera angle so if cars are occupying all 3 lanes they aren't counted incorrectly. From there I just need to detect cars as they pass and count them.

It's really cool to see it used like this! The resulting images are really neat as well!