I purchased and tested the Seattle Sports Dry Doc Digi Case. The Digi Case 02 appears to be the same case with different attachment device.
I filled the case with a paper towel and then submerged it for 30 minutes in 1 foot of water. The end of the paper towel was slightly moist when I recovered. Most phones, even an iPhone, would probably still be ok at that point.
It looks to me like a new Digi Case, carefully sealed, would protect against a quick dunk. This one is fine for keeping my phone in a non-waterproof bike bag or for insurance on a hiking trip that could involve a stream crossing. I would want something more robust (and more costly) if I were going on a canoe trip.
An iPhone is useable through the case -- the touch controls work.