Thanks for your help guys. I now have mupen64plus working well with Accelemymote on both SM64 and MarioKart 64. I had an error with no graphic plug in selected, but that was obvious to fix. Then once the ROM was started, it remained at the GUI whilst playing the game sounds, with no way to access the visuals. That's sorted itself out.

My girlfriend now hates her iPhone 3G S and wants an N900.