This is a neat idea. Have you ever had your cell phone battery die on you just as you needed it? I think we all have. Designers Song Teaho and Hyejin Lee may have a solution for us.
Their concept battery allows you to charge it by winding it up with a few turns of your index finger. It should give you enough battery life to make a quick call. According to the designers, 130 revolutions should give you 25 minutes of stand-by time or enough juice for a 2 minute call.