I would opt for a simple waterproof bag and get a phone that has the features you really want or need. We sell all kinds of bag right here on this site. For example, look at this one:
http://store.catsailor.com/tek9.asp?pg=products&specific=jnpoqnfpn8I just got a new phone before the Tybee 500 and was able to use it for covering the race uploading pix and stories. It was capable of 900K download, which is faster than our DSL at Put-in-Bay.
I doubt that waterproof phone will do anything like that.
Rick