This is what I think of an iPod touch controller... A playststion controller or a logitech controller (Probably PS3 controller since it already work as a gamepad on windows, with some drivers) that has a wire going from it to a dock connector plug that goes on the iPod. With that, you either use the dock to stand it up or use you lap to stand it up. You would port drivers over to the iPod... And make the buttons ned something like "1" etc... And you would configure the buttons on the emulator itself... that's if the emulator had already be compatible with the controller. The iPod would just show the video full screen and you would use the contoller to play... If I was really really good at this stuff... I would do it, and... keep it to myself.
motors? What? I made a working button, using a lever and tinfoil. Super simple. Now I'm just trying to make frame to mount a controller on. Its only half as thick more, covers about 50 pixels; and doesn't stick over any edge. Pictures when I get home.