Remember Minority Report? If so, what about that scene where Tom Cruise is controlling a computer with hand movements that synced up to opera music? If your memory is fuzzy see it here. Well, the computer from that scene is actually a reality and has been in development since the early 90s. Who knew?
Oblong Industries, the developer of the g-speak spatial operating environment, actually worked on the set of Minority Report so there is a reason for the similarities between the machines.
The whole thing works with an I/O bulb, which looks out at the world and can tell the computation device what is going on in the room. Finger and hand motions are tracked in order to control the computer. Even two-handed and multi-user inputs are recognized by the bulb. But to really explain it… you need to watch the above video. It is pretty astounding to see in action.