Skinput: Appropriating the Body as an Input Surface

I have been seeing a lot of buzz recently about Skinput (watch the video if you want to understand it), but basically it sensors that listen for acoustic transmission from gestures (i.e.: tapping, snapping, etc.) you can make on your arm. From this information, you can navigate portable electronic devices (such as: smart phone/PDA, MP3 player, etc).

This technology is similar, but totally different from another technology from SixthSense. see the following TED Talk for more information.