In my experience with alternative chargers (and just equipment in general) usually something that claims to have that many features and costs that little is pretty much a waste of money. Contrary to what some may think, Solar equipment (especially efficient/useful solar equipment) is not cheap. Yes, you can buy a tiny solar panel that puts out 1W at 0.5V for about $5, but it's worthless for anything but powering an LED (which begs the question... without a battery why would I want to power an LED with daylight?).

I've tried a few hand-crank type devices and there it's simply a matter of practicality, especially for the tablets. Depending on the make and model it's possible to use them to generate sufficient power to at least keep the tablet running (don't even think about using them charge it from the off state) but how useful is a tablet after spending 5 minutes cranking a dynamo so you can get an extra 30 seconds of power out of it? Cranks are great for extremely low power devices, but as efficient as our NITs are, they certainly aren't "three ultra-bright LED" efficient...

It's also important to keep in mind that the NITs themselves require a certain amount of current to even engage the charging mechanism to let you power the battery (whether the tablet's on or not!), which I believe is somewhere around 500mA or higher (could be wrong), which most alternative chargers won't put out. The only one that I've found to be effective is the Solios because they have their own internal battery that the solar cells charge directly, and so as long as the battery has sufficient power it can provide enough current to actively engage the NIT charging circuits (the panels on the Solios are also much more efficient than the lower end guys). Cool device, but it's not cheap, so you have to think about your application and see if you can justify the costs.

-Rob