Soldius 1 Solar Charger
I just had this problem the other day. I was out and about trying to meet someone and my cell phone died. So I could either buy something I didn't want at a coffee shop and sit there while it charged, or I could have had a solar charger because you know, the sun is everywhere.
"The HiJack is a very simple little device. It plugs into your headphone jack and splits it into two jacks. What makes the HiJack so sweet is it's tiny size and keychain clip, so you can keep it with you wherever you go."
I idea of something like these seem incredibly sci-fi or some half-witted attempt to be futuristic from 1987. But no, these are actually real and work and are pretty awesome.