It’s simple because cable releases are simple devices – they usually have two contacts: a focus contact and a release contact. Closing one contact will trigger the internal focus mechanism and closing the other contact will release the shutter. In fact, its so simple that you can make one from a dead mouse.
What release cables usually lack is brains. I mean they will trigger a camera when you tell them, and some o the mode advanced models even have HDR, BULB and timelapse modes, but they cant act upon external events.
This is where triggertrap mobile comes in. It harnesses the computer and the huge array of sensors of the iPhone to trigger your camera upon shake, noise (clap), presence of magnets or metal (god knows what is the application for that), face recognition and a few others. It also allows for timelapse capture (with a road trip GPS based travel mode) and HDR.
You do need to buy a special dongle ($10) and a dedicated cable ($10) to interface the app with the camera but $30 total (app+cable+dongle) is roughly what a medium level release cable will cost regardless.
I played around with an early production unit and was very happy with it. The build is reasonably solid and it has a very small footprint in the bag (without the iDevice).
You can watch the introduction video followed by a demo below: