http://www.smh.com.au/news/articles/its-an-eye-pod--wink-wink/2008/03/04/1204402401441.html
The system, comprising a single-chip computer and a couple of infrared sensors, monitors movements of the temple and is so tiny that it can be built into the side of a pair of eyeglasses.
Closing both eyes for one second starts an iPod, while blinking again stops the machine. A wink with the right eye makes the machine skip to the next tune while with a wink of the left eye it goes back.