At only 3.25″ X 2″ and weighing about an ounce, the DigiPower ChargeCard is small enough to fit in your wallet. This emergency power supply from Mizco is available in iPhone and universal smartphone models. The cards have a leather-like finish and are available in black, red, or white. They have a fold-away cable, and the high-capacity batteries offer about a 25% power boost when you are away from an outlet. The universal smartphone version is only 1/8″ thick, but it holds a 680mAh battery pack that can add about 2 hours to your smartphone. It costs $29.99. The Apple iPhone-specific model isn’t shown on the website yet, but it’s said to be 1/4″ thick and has 720mAh for 2 additional hours of power.