It looks like a sound trigger for flash. Am I right Don?
WE were using the TriggerTrap flash adapter to fire the flash. It was triggered by the BB gun we used to pop the flash. The cameras were set on bulb. 3 flash units all set to 1/128 power to get the shortest flash duration we could get.
Some of the balloons were filled with plain water, some had glitter in them (these can out the best) and a couple filled with shaving cream.
We will probably do this at least one more time with a few variations with the contents of the balloon. Coke, just glitter, colored powder and whatever else we think might be interesting.