- Tiny Monster Handheld (totally not a pokedex or a digivice): Use a Raspberry Pi 0W or an ESP8266 wifi development board. Hook it up to a 90s Nokia brick phone screen. Write some basic code to govern behavior, draw some sprites, make a simple Training game, make a wifi battle game, maybe do some Augmented Reality stuff. Basically P O X for the modern age.
Then: (Considered/Suspended)
Now: I never built this, but I actually did prototype it out. Used an ESP8266. Got it working with the old Nokia brick phone screen. Coded up a basic battle system. It was cute, but Pokemon Go already existed, so there was no need for it, and I was solving the problem at the wrong level.