Since 2002, the film Minority Report has inspired computer geeks the world over. At the time, touch interfaces were relatively rare, and where they did exist, they were typically limited to one finger at a time. In the film, Tom Cruise's character famously interacts with his computer by standing in front of a projected screen and basically waving his hands at it, manipulating objects without even touching them. In the film, computers had lept past mere touch, and moved to gestures, performed in the air.
In the years since, we've seen some impressive strides in computer interfaces that begin to approach the "Minority Report computer," as it were. Our own fearless leader Mangesh talked up what would become the Microsoft Surface as an Amazing Interactive Table in May, 2007. But that required actually touching the table. Earlier this year, I pointed to a TED Talk in which John Underkoffler, designer of the "Minority Report computer," gave us a demo of a mostly-working system that works today (though it did crash once).
The latest giant leap in "Minority Report computing" comes from an MIT group (read more in the YouTube description here -- credit to my LIS brethren!). To make a long, geeky story short, they adapted (er, hacked) a Microsoft Kinect sensor, hooked it up to a robotics system, and made their own "Minority Report computer." Again, it's not perfect, but given that they're using off-the-shelf hardware and free, open-source software...2002's future is now. (Note: there is no sound in this video.)
See also: Kinect Hack Makes Shadow Puppets Real(ish).