Pick up an iPhone 4/4S/5 Bracelet Charger Cable in your choice of 11 styles for just $8.99. Shipping is just $1.99 and you can buy up to 3 without the shipping going up.
These will charge iPhone 3G/3GS/4/4S/5, iPods and iPads; Android; any micro USB device.
I personally love this idea. My daughter is in college and last year forgot to take her phone charger back with her. She wound up buying a new charger but this would have been a great way for her to always have a charger with her. They're cute, too!