Hi DJ,
I use the OB waterproof ipod case purchased from BFC. To make sure I didn't wreck my iphone the sales person suggested I test waterproofness first. I stuffed the pouch with paper and took a long bubble bath, periodically pushing the pouch to the bottom and holding it there. No water through to the paper so I have been using it out on the boards ever since.
As Coast said, The pouch floats as it has air-filled panels around the edge and it has an earphone jack out the bottom. I have never used the earphone jack, and due to the rough treatment I give the pouch (throwing it in the wet buckets in the van etc) I reckon the jack is the most likely failure point. It is already looking a little dodgy in that area (after about 6 months): might have to take another bath?
I don't like a phone call ruining my paddle & would rather the sounds of the environment than music when paddling, but when we have clients out on the water it is a policy requirement that we have some communication in case of emergencies. It is also great to call ahead to make sure the 'horse & carriage' is on site waiting to take the clients on the second half of their 'tour'. (no pimping!).
I can easily use the touch screen and hear through the plastic, but a little hard to read text messages and not possible to take photos as the back of the pouch is solid white. I attach it to the shoulder strap of my camel pack with a big clip.