I'm currently in the process of researching the home brews. From what I've gathered, you can build one reletively simple, or get fancy with it. Also, most claim they are a much better product than the commercial ones. Features like extended battery life, a trail mode to get multiple pics, 2 sec trigger times are a few things that are mentioned frequently.

The biggest issue is finding a compatible camera. Ebay is the usual source, except its evident that many are doing the same thing and driving the prices of the camera's up. The most popular camera is the Sony P41 or P42 camera's. They're easy to modify and have extremely fast triggers.If you snag one of those for 75.00 off ebay, and use a pixcontroller kit, you can build an excellent digital for less than 175. This camera is reportedly getting approx 1 month out ofset of batteries and has a 2 second trigger time.