I've gotten PocketUAE running on my Windows Mobile pda and it's lots of fun but my PDA has a keyboard (google HTC Universal - it's practically a 5" laptop) - albeit with limited keys. The Pocket UAE launcher already lets me map any of the keys to left/right mouse but it'd be nice to be able to map any of my device's physical keys to any amiga keyboard key. This would allow me to set up a nice config for (for example) bloodwych, allowing me to map the arrow and turn keys to allow me to move around, and the function keys to allow me to load/save. This way i could wrap configs for each app/game that have the keys mapped as i want them and just launch.
I can see this being expanded into a generic model for any pda/mobile, imagine being able to play xenon 2 on your mobile and being able to remap the joystick to 2468 with the mp3-player button at the top left of the phone being fire... nice :-)