MyFC has created PowerTrekk, which is a nifty little device that can charge your phone using ordinary water. It doesn't even have to be clean water, so no worries about wasting your good water supply if you're out in the middle of nowhere on a hiking trail. It also works with either fresh or seawater, so as long as you don't use water with a bunch of sediment in it you should be good to go. The water itself doesn't actually charge the device, but instead there is a PowerPukk inside that uses the water to generate electricity, which is then stored on-board for later use. Internal storage will hold up to 1600mAh, and it is capable of giving back 1000mAh.
The way this works is you pour plain water into the disposable PowerPukk, which then releases hydrogen gas to combine with oxygen (H2O, you know). From there, the chemical energy is converted to electrical energy to the tune of enough to at least power an iPhone to 25%, if not all the way to 100%. What you're getting here is your own personal fuel cell, which was originally developed to be used in cars (and they're still developing those). It is faster and more reliable than a solar charger, which usually requires some ungodly number of hours of direct sunlight to fully charge, so that's good.
Here's the catch. You're going to have to shell out about $230.00 US for one of these. See what I mean about weighing your options?