I just met Rob Wang, a computer vision researcher who recently graduated from MIT. He’s showed me a video of a two-camera gesture tracking system that is able to track a users thumbs (and by extension, hands) above a black desk surface. No other special hardware needed.
He is moving out to the Bay Area to work on the technology. He has some demos of a slightly different technology based on a multicolored glove online at his website, 3Gear
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