This was an experiment I did with Mike G last year, using three light sensors, a light box and a phidgets board. The light sensors are reading the absence of light (from your hand) to move the panorama left and right. To initiate a "link," the hand is moved to the back of the box. This is when you see the "this car is ugly."
A later test using infrared sensors worked much better (will post this soon). It didn't get fussy about light.
This initial test proved that an interface could work without touching and that interaction was possible. I then moved on to the infrared sensors, which cost about $30 more!