Related:
Chargebite, iPhone, iPad
Now up on Indiegogo, ChargeBite is a brand new type of iPhone charger that charges your iPhone by transferring power from your friends' iPhones or iPads. The promo proclaims "It's beautifully designed, extremely practical and will completely change the way you think about chargers. Simply connect yours and your friends' iPhones to their designated ports, and that's it --- charging is on."
Check out the video below, or the campaign here.

There are a lot of charging solutions out there: chargers based on sunlight, movement, thermoelectric effect, external battery and juice pack cases. Each one is restricted by various constraints. While some require sunlight, others need to be pre-charged.
What's ChargeBite constraint you ask?
ChargeBite just needs 2 friends! No precharging, no cables and no other special requirement.
Whether you're in a pub, hanging out with some friends, eating at a restaurant or relaxing on the beach, as your iPhone runs out just look in the eyes of your responsible friends and smile embarrassedly... They'll probably agree to share some good ol' precious energy if you ask them nicely :)