The $100 price point of the flash controller kit is a bit prohibitive as I am a PSCS (poor starving college student - I'm coining the acronym now). However, I found this kit on gibson tech: http://www.gibsonteched.com/R-VS1.html
which looks like it might be perfect for the application. What do you guys think?
Depends on the latency, I suppose. This idea actually popped into my head in the shower a few months back. I thought of a VOX kit to operate the shutter on my cheap pentax to get pics of stuff hitting the ground. Namely, breakable stuff - the loud noise triggering the shutter. Sounds cool.
What about tapping the hot shoe on your camera (if it has one) to actually trigger the event you want to capture? For example, you could have the shoe trigger a solenoid (or some other mechanical arrangement) that pushed a pin into a balloon. You could try rear curtain sync (again, your camera has to support this) to delay the flash slightly.
The advantage of this approach is that it can probably be done inexpensively using parts culled from eBay.
You could probably rig something up to pop the balloon when you press the shutter, but it's a horribly inefficient way to do it. Not only would you need to build a circuit that is probably just as complicated as the sound sensor described in the link above, you would also have to build the actual mechanism to pop the balloon. The other flaw is that while your mechanism would work fine to pop a balloon, it would not allow you to (for example) photopraph a breaking glass which the sound circuit would do.
It would definitely be a cool hack, but probably not of to much practical value,