At this years E3 Gaming conference, Microsoft has unveiled the controlless game device called the Kinect. It's targeted at the Nintendo Wii with its gaming accessibility allowing novice gamers and expert gamers into the fray but without the Wii joystick that could possibly fly out of one's hand and knock someone unconscious.
Then again one could still accidentally (or even intentionally punch a trespassing observer if they get too close to the person practicing the boxing simulation game.
http://www.xbox.com/en-US/kinect?WT.srch=1
http://reviews.cnet.com/8301-21539_7-20007570-10391702.html