don't know if this belongs here,but it could be useful and it doesn't take that much gear.
http://laughingsquid.com/how-to-charge-a-smartphone-with-a-9v-battery-car-charger-and-a-key/
http://laughingsquid.com/how-to-charge-a-smartphone-with-a-9v-battery-car-charger-and-a-key/