I would love to be able to write a game that can netplay with other Playdates. Even just having the ability to do http GET and POST requests would already open up a lot (such as leaderboards). A unified way to start a netplay session with another playdate (via bluetooth or internet through a room code or something) would be even better.
It would also be awesome if this could be exposed to Pulp too, as an "advanced" feature. I've been writing a clone of Tetris Attack in pulp, and while 1-player mode is already entertaining, I'd love to add a 2-player mode as well.