You can charge your phone using your body electricity by making a capacitor using items commonly found in your pocket.
You need two silver coins, a paper clip, a piece of paper, your charging cable and of course your phone.
The electricity from your body is stored in the capacitor and then sent to the phone to charge it.
The coins act as a two plates of a capacitor and the air gap and the paper act as the insulator (dielectric). The paper clip is to connect inside of your usb connector to the outer plate of the capacitor. Have fun! Try it out.