This thing is way out of my price range, but that doesn't mean I can't think about having one. The Solar Panel Backpack (very original, Ralph) in the RLX line is… well, it's a backpack with a solar panel on it.
The material isn't specified, and I can't really identify it, but they say it's water-resistant. I doubt you can go diving in it, but it should handle rain, spray, and maybe a quick dip with ease.
The solar panel produces a little over 3 watts, which isn't a lot, but could be enough to put a little juice in your phone. It comes with a battery unit that you can charge up, so you don't always have to have your device plugged directly in.
Too bad it costs $800. Ah well! I'll keep my bindle, I guess.