The upcoming movie In Time features digital clocks embedded in the skin; but imagine that instead of showing your life ticking, the image was part of your phone's interface. Need to make a call? Just dial it up on the palm of your hand.
Chris Harrison, a PhD student at the Human-Computer Interaction Institute at Carnegie Mellon University, and a fellow at Microsoft Research, came up with a wearable device that projects an image onto a surface, which then doubles as a touch screen.
Called Omnitouch, the system uses a shoulder-mounted device that both a camera and projector. The camera images your fingers and builds a three-dimensional map of them. Then the software builds a kind of skeletal diagram that shows where the fingertip is. To detect a "click" the camera looks for areas of the finger that are in contact with a surface. (The only time it doesn't work is if the area the finger is in is outside the camera's view).
The second part of the system is the projection. A pico-projector can send an image out without losing focus even at relatively large distances, and this also reduces the size of the unit.
The system is a little cumbersome, but it does allow you to dial numbers on your hand, pull down menus on your arm or even type on a virtual keyboard that appears on a wall or table.