Researchers at the University of Tokyo's Ishikawa-Komuro Lab have developed a system of motion tracking for cellphones that brings a little Project Natal magic to your handset. Using a high-framerate camera attachment, the software can track the position of a finger held in front of the phone in 3D space, registering distance as well as fast-movement "clicks".
Video demo after the cut
It's not the first time we've seen cellphone cameras used to track movement and translate it into touch-free control. Sony Ericsson have used motion-tracking both for gaming and for alarm/call control, though neither system was as accurate as the University of Tokyo's implementation.
Theirs is capable of tracking movement across an on-screen QWERTY keyboard, selecting characters with a click-movement, together with allowing for contactless scrolling and even drawing on-screen. We saw a similar demonstration at MWC 2010 back in February, where Texas Instruments showed an OMAP3-based device using a regular webcam to track 3D gestures.