Let me fill you in on the Sony Waterproof Walkman. It has been a long time since this company has been at the top of the heap for portable audio devices, but I think they may soon reign supreme once more.
The Sony Waterproof Walkman does exactly what you would expect it to -- it functions in wet environments. Whether in the rain, covered by sweat, or even amidst a full shower, this thing will not quit. Probably the coolest feature of it though, is something called "Smart Mood." This puts songs on shuffle that are related to one another in terms of style, so the vibe will never get killed mid workout.