Microsoft's TouchWall system basically consists of three infrared lasers, an infrared camera, rear projector, and Plex software running on a Vista-powered PC. It turns just about any flat surface into a multi-touch display. Video preview after the break. Click here for first picture in gallery.
A camera notes when something breaks through the laser line and feeds that information back to the Plex software. Early prototypes, say Pratley and Sands, were made, simply, on a cardboard screen.[via CrunchGear]