The link goes to the kind of products I'm talking about - batteries that could fill a phone and are able to be charge on solar.
The more I backpack the more I like the idea of this kind of device. The pragmatic parent in me justifies it as a safety measure in case I get hopelessly lost. The real reason I want it is because I like to take pictures but hate having to wait for my phone to power up to do so.
I'm wondering if there's either
a) Owners of such a device that could tell me about it or
b) People who understand solar well enough to tell me if such a small cell could really result in any kind of substantial charge.