I am not sure if this belongs in off topic but I know it's a safe place to put it.
Like some of my other posts please treat this as a thought experiment
If you feel like you need to post that you think it's not needed please feel free to keep your comments to yourself.
I have been wondering about field use of the RPi and there's been loads of discussion about battery and solar powered supplyied and in car RPi operation.
Given the nature of the beast and its operation I have been considering the use of Freeplay equipment, and given I can run my RPi headless from my laptop over Wi-fi I have been considering camping uses and my thoughts driffted back to my Freeplay Radio. That brilliant flash that kicked Trevor Baylis into the perception of the British Populus.
I know the original had a simple 3v output and that these devices have moved on a long way from the original concept.
In the light of those thoughts of camping use I have been thinking about a wind up USB hub with a couple of 10BaseT ports on for good measure.
The device could also be used for charging mobile phones.
After some consideration I decided you would need a small battery or capacitence driven audio warning so that you would know when to rewind before the power dropped bellow a level to sustain your RPi. Internet access is not an option as I am considering this for locations where internet coverage is at best patchy and at worst non existent.
But I am looking to the child enjoying a holiday in the UK subject to vagaries of British weather isolated in a caravan with a Rpi a laptop and time to tinker.