I have seen a lot of interesting accessories for the iPhone that can make it ready for extreme conditions, like skiing or snowboarding. I suppose since people are using their iPhones for all kinds of environments need this type of protection.
For example, there is the driSuit endurance, which is designed so you can submerge the iPhone in water. This is especially handy for situations when you want to use the camera or video under water. I am not certain how deep you want to go, but if you want to listen to music, it has an integrated waterproof headphone jack.
Another feature is the “fluidic touchscreen membrane” which looks like there is liquid on the touchscreen, which will allow the user to run all sorts of apps on the touchscreen itself.
Those two features would be enough to sell the product, but the driSuit Endurance also has a place to stash a credit card, which is starting to become a standard feature on an iPhone case.
You can purchase the Endurance case for the iPhone 4/4S for about $59.95 or pre-order the iPhone 5 model for $69.95 on the driSuit site.