Check out the thinnest lightning cable on the market today. The ChargeCard puts your iPhone 5 charger in your wallet so you always have it with you. It is slightly thicker than a credit card and allows you to charge your devices from any USB port.
"Our quest was simple: a charging cable for your iPhone 5 portable enough for you to always have it on you. The ChargeCard fits naturally into your wallet. It's there when you need it, and out of your way when you don't. "
The ChargeCard is available for pre-order for $25, with delivery in May. They also have microUSB and an iPhone 4 version too!