Radar-like sensors bring touch sensitivity to everyday items | The Verge
http://www.theverge.com/2011/11/1/2529957/radar-like-sensors-bring-touch-sensitivity-to-everyday-items
Utilizing a technology known as time domain reflectometry, a pulse is sent through a wire every time it's touched until it hits a detector, which reflects the pulse back. Based on the speed of the pulse and the time it takes to return, software can pinpoint the starting point of the pulse. The touch-sensitive wire can be placed onto any regular item — the wire can even take the place of a guitar string, while a wire pattern can be embedded inside deformable objects like clothes.