One of my hobbies is embedded electronics. I was thinking of how cities/municipalities/etc pay a lot of “meter maids” to go around and ticket parking offenses, and how it really should be automated. This way you could eliminate most of them (but not all) and increase revenue at the same time. Of course if you park at meters you probably won’t like this prototype I’ve made.
Back in 2009, I used to own a laundromat. It was a self-service unattended laundromat that was still coin-op, no card system. I wanted to know how much traffic my laundromat was getting, to see busy times of day and get some metrics without having to be there. Thus spawned a little invention of mine, the laundromat watcher.