Maybe the Aerobic Keyboard is a little closer to realization. An article on the front page of yesterday's New York Times talks about how hardware and software have progressed to the point where controlling electronic devices by gestures may soon become common.
And this site describes an experimental project (still in existence?) that effectively lets you use your body as a joystick to move through Second Life.
Computer users of the world, arise! You have nothing to lose but your flab!