Hi Tyler!
The wildest thing I made was with a friend for a hackathon. We created a website that took your daily step / distance data from your fitness band, and mapped that to progress in Super Mario World. Each day, you'd sync your device and it'd play through a comparable distance of the game in front of your eyes. The idea was to eventually walk / run yourself through the entire game. It was meant to encourage more steps to be taken in your day.
The wildest thing I want to make is a mesh connected set of tiny devices mounted on a wall with screens and speakers, that all know about each other and work together to make a game you play by communicating with them. I've started planning the schematic for the devices but haven't moved further on this yet!