The cheap solar chargers I've toyed with haven't been remotely worth the money. If mobile solar is part of your strategy, get a good one that either charges its own onboard battery (which you can then use to charge your device) or charges AA batteries that your device can use.

Crank-based chargers might be good enough to send a quick text message or 911 call, but as a charging strategy for other use they leave a lot to be desired.