So custom game controllers are getting pretty common ... at least in the console space.
Guitars, Dance mats, drums, Wii, ...
My own take on this:
There should be a furry stuffed animal controller. Somewhat like a
It should be able to register different kinds of petting.
Of course it should also be able to purr in sound and motion.
Haven't quite thought of a game to use it in yet admittedly.