It’s not a portable backup battery to feed your iOS devices out of juice, but if you want more conveniently way to connect your iPhone with backup battery, the following ChargeCard credit card shaped charging cable will help you.
ChargeCard is an ultra portable USB charging cable that measures 3.25 x 2 x 0.1″ inches, and designed for iOS devices. As we can see from the images, the USB cable is shaped as a credit card in order that you can conveniently put it into your wallet, purse or pocket for portability. When you need it, you can take it out, and folding out the middle USB arm to connect with your backup battery, while the integrated 30-pin connector on the edge lets you connect the USB charging cable for charging. Apart from that, the body of the USB charging cable is made from ABS plastic, while the USB arm is made of flexible thermoplastic elastomer, and the charging cable is compatible various protective cases.
At present, the designer of ChargeCard is raising fund on Kickstarter. Pledge $20 will let you own the credit card shaped USB charging cable. If you’re interested, jump to Kickstarter for more details. Update (8.21/13): ChargeCard is available at Photojojo for $25 at present.
Additionally, if you need other options, you might like to check Twig charging & sync cable and more via “charging cable” tag.