Thanks guys for the replies. I had read that thread on the Exile a while back, but didn't know it wasn't out yet. Guess that explains why I couldn't find it on their site. I don't really need it until July, so maybe Brian will chime in.
I might give this one a try if nobody else has any recommendations. I like the fact that it can run on its own via internal Li-Ion battery (up to 8 hours) or while charging via USB. I can't imagine needing more than a few hours at a time. Sounds like the 4s has a decent range since it's Bluetooth 4.0, so I'm hoping this will do the trick.
If anybody else has anything to add, much appreciated.