I needed a foot switch for my DSLR camera so that I could take hands-free pictures. On a long-shot, I went down to the local Radioshack to see if they had one. As expected, they didn't have any camera foot switches, but I did luck out that they had all the parts necessary to build my own. Here is how to throw together a 5-minute camera foot switch with easily obtainable parts from Radioshack.
Step 1: Go get stuff
You will need:
(x1) 3/32" Mono Plug (part # 274-0289)
(x1) Sustain Foot Pedal (part # 42-4053)
(x1) 20' Stereo 1/4" female to 1/8" male Cable (part # 42-2561)