BreachBangClear has done a cool piece on a hefty ruggedized power-pack for charging his devices out in the field, for extended times.
Here's the link to his take on the PowerTravellers - Power Gorilla. This tablet sized battery boasts 20,000 mAh of charge, and you can see that Kevin put it through its paces in some pretty rough conditions.
I've covered a couple of power-generation devices in past, the thermoelectric Tellurex-tPod1, and a wish lust BioLight campstove to generate power, solar systems like those found on the SLXtreme iPhone case and the other small solar systems I have tried
but as yet haven't really covered how to STORE that power, other than in those built-in devices. Worth checking out Kevin's findings, for sure!