Thomas Clauser writes:

The LighTouch (http://wolfebaine.blogspot.com/2013/03/lightouch.html) is a ‘touchless’ music player based on Arduino that is controlled by ultrasonic sensor. The distance of your hand determines pause/play, volume control, or next track.

From the project page:

LighTouch was an idea I had as I was just diving into Arduino. Like anyone getting started, I bought an Uno and three random shields just to play with (music shield, bluetooth, and ultrasonic range finder). To that end, I got each of them up and running in record time and got bored. So what was the next logical step? Right… figure out how many of these shields can I use at the same time. In this case, a music shield and ultrasonic range finder made the cut.

The idea is pretty simple; an mp3 player that you never have to touch. Simply hold your hand over the device to adjust volume, pause, and move to the next track. All the commands basically key on the distance of your hand from the sensor.

Photos and more here!