I own several android and iOS devices which just lay down at the bottom of a drawer. I'd like to make an use of them. What are you using your retired devices for? Surveillance cameras? Time lapse? WiFi scanners, anything else? I'm looking for projects that I can make with my kids ;-)
Kids. I have a great idea but no one to play them with.<p>You can make a game that runs on all the phones and uses motion sensors and knows the relative ordering of players. Imagine hungry, hungry hippos (or other game idea) with each phone being the controller. You could even put an iPad in the middle for a shared display.<p>You could play cards with the hand being dealt to each phone and the iPad showing common cards.<p>Edit: I'd try to use Flutter/Dart to target both Android/iOS using a reasonable language/api with some native functions being in Java/Kotlin and Swift.