Microsoft Research showed off a cool project named SoundWave at CHI 2012. Watch the video demonstration below.
SoundWave uses the Doppler Effect to sense gestures by just using the standard speakers and the microphone found in a laptop. SoundWave work of Sidhant Gupta and Shwetak N. Patel of MSR and the University of Washington along with Dan Morris and Desney Tan.
The Doppler Effect characterizes the frequency change of a sound wave as a listener moves toward or away from the source and the team found that it could be used to measure movement, direction, velocity and size of a moving object. With this the system is able a series of hand gestures that could be recognized by existing hardware. More details on Next at Microsoft. Via The Verge.
What I like most about this is that there is no additional hardware. It is just software and can work on any laptop right away. This should be enough for Microsoft to push this project into a production feature. Watch the video below.