I'm not too sure how unusual it is, but I have a satellite tracker on a pi 3 b+ based on satnogs. It helps other scientists get data out of cutsats and other satellites. It's pretty easy to set up once you know what to set up.

I once had a butler program on a pi 1 with WiFi chip back around 10+ years ago. No ai, just a bunch of batch scripts + espeak. It was a cool project that would tell us the weather, time, any to-do items, and internet usage ( att had a hard limit of 100gb and I used a script tu tell how much we used per month). Ran for a couple of years and then disassembled it. Still have the GitHub repo. This was many years before Alexa, Google, and the other such projects. It wasn't better at all (espeak sounds so robotic, even when tweaked).

I ran a Bitcoin miner on a pi and made -$4.50ish a month back a decade ago. It was my most popular wiki pages back when I self hosted one. People were really interested, but it never made any money. It was more of a proof of concept . It's pretty easy to compile, but hard to track down all the dependencies. That was waaaay before the asci miners came into play.