The mods on this website are impressive.
In about 3 minutes of browsing I witnessed an ipod pulled out of a kidrobot munny doll head and plugged it into an NES controller to play DOOM.
Then I watched a video as he used a tilt sensor to control a car game on Gameboy DS.
You can find more on Acidmods site or on youtube including PSP mods and others.
I think I want that ipod dock on my desk.