An anonymous reader sends this news from the University of Washington: "[C]omputer scientists have built a low-cost gesture recognition system that runs without batteries and lets users control their electronic devices hidden from sight with simple hand movements. The prototype, called 'AllSee,' uses existing TV signals as both a power source and the means for detecting a user's gesture command (PDF). 'This is the first gesture recognition system that can be implemented for less than a dollar and doesn't require a battery,' said Shyam Gollakota, a UW assistant professor of computer science and engineering. 'You can leverage TV signals both as a source of power and as a source of gesture recognition.' The researchers built a small sensor that can be placed on an electronic device such as a smartphone. The sensor uses an ultra-low-power receiver to extract and classify gesture information from wireless transmissions around us. When a person gestures with the hand, it changes the amplitude of the wireless signals in the air. The AllSee sensors then recognize unique amplitude changes created by specific gestures."