If you got a Nintendo Wii for Christmas, then you'll enjoy this cool video:

"Head Tracking for Desktop VR Displays using the Wii Remote"

Using the infrared camera in the Wii remote and a head mounted sensor bar (two IR LEDs), you can accurately track the location of your head and render view dependent images on the screen. This effectively transforms your display into a portal to a virtual environment. The display properly reacts to head and body movement as if it were a real window creating a realistic illusion of depth and space. By Johnny Chung Lee, Carnegie Mellon University. For more information and software visit http://johnnylee.net

(Via Vik Rubenfeld.)