Kinect (PC source) running custom software to scan/track objects. In this case, lightsaber While not incredibly impressive, its neat and some guy put this together in a matter of days. I'm eager to see what full development studios can do over the next year or two.
http://www.youtube.com/watch?v=3EeJCln5KYg&feature=player_embedded
http://www.youtube.com/watch?v=3EeJCln5KYg&feature=player_embedded