I actually own a solar panel-backed mobe just for having something robust and nearly-always-available on hand, as a back-up. Too bad the panel doesn't generate enough power to actually charge the phone, making it but a toy. And, of course, the thing goes a bit wonky when it's been in the sun for a while. Doesn't seem to take the heat very well.
I like the form-factor of that "John's Phone" much better. Why not use that form and stick an extra large antenna and two (or four) AA batteries in?
Or that juice (sugar and water mostly, I recall) powered concept phone, with a less artsy fartsy shape; more something that fits in a spare pocket and you can store some fuel in before adding the water.
Somehow these things remain the toys of designers, possibly because they're not even trying to use them, nevermind in some sort of needful condition. Which is a pity, for then their toys remain but trinkets. Yet we have a lot of technology that could make these things actually useful. So get to it, designers. Or do I have to write the vision statement for you, eh?