Need a foot pedal for your Mac? Got a two switch guitar pedal and and arduino board lying around? A couple of wires, a three prong 1/4" jack and you're all set. I had to do some audio transcription and used my pedal to play/pause and skip back the video.
This tutorial illustrates making a foot pedal for a Macintosh computer using an Arduino and a 2 switch guitar amp pedal.
You'll have to be a little familiar with soldering and writing simple code.
If you need a guitar amp pedal switch, you can buy one or make one with this other instructable
or with this one