[Tobe] has an intervalometer for his camera, but he wanted a device that could trigger the shutter using several different methods, not just time. He calls his creation the Megavallometer, which can utilize any one of three distinct criteria.
He recently purchased an Arduino and a couple of shields, so he figured this would be a perfect project in which to use them. He hooked up a microphone and a photodiode to the Arduino, allowing him to use both sound and light to trigger his camera, depending on which mode he selects. Of course, the Megavallometer still incorporates the functionality of a standard intervalometer as well.
Once connected to his camera he selects one of the three trigger programs, and the Arduino handles the rest. If either the light or sound triggers are selected, the respective sensors measure the ambient levels upon selection, allowing for accurate results in any setting.
While the Megavallometer is a bit larger than other intervalometers we have seen, it looks incredibly useful and can likely be strapped to a tripod or similar if need be.
If you have a minute, be sure to check out the video on his site for a sneak peak if his Megavallometer in action.