Rigged an exercise bike up to an old Super Nintendo controller using An Arduino microcontroller, some sensors/switches and some transistors.
Peddling at a certain rate holds down the A button to accelerate, left and right are buttons on the handlebars and there is a red button in the middle of the handlebars for using special items.
I have another video I'll upload soon which better describes the bike controller.
There is a quick overview of how it works here:
http://statuswoe.blogspot.ca/2012/04/super-mario-kart-cycle.html including a link to the github project where my very quickly written android sketch is available. I'm hoping to put up schematics of both the bike and SNES Adapter (part of which actually uses an SNES controller) there when I get the chance.
For anyone interested in seeing it work with a non-SNES game Mike McGraw and I came up with a game/adapter that is played on a Computer via USB. I think the game is pretty neat.