The newer versions of MAME can emulate Tamagotchi devices, but I'm not sure about Digimon. If not, new LCD games are being added all the time, so it may just be a matter of time. As far as RetroPie is concerned, running the newer versions of MAME would normally be a bad idea, as performance would be terrible. However, LCD games like these might not demand as much to run well. It'd be a great experiment. Here's an article discussing the games being added to MAME's repertoire and below is a video to see a few of them in action.
