The Game Boy Zero (GBZ) is one of the pinnacles of Game Boy modding. This system uses a Raspberry Pi Zero to run a variety of emulated games and has many more capabilities than your old brick DMG. Add another set of buttons and some hard work to make the ultimate Game Boy.
Check out our good friends over at SUDOMOD for anything and everything related to the Game Boy Zero. GBZ forums form sudo mod are a great place to get connected.