The guys at Native Union have put on a Kickstarter project called JUMP, a charge cable with its own built-in battery pack. It can detect when your device is at full power, and will then begin storing some power on its own, enough to charge an iPhone up to 30% when it's needed most. When you're done using it, the cable wraps neatly around the battery pack and stores easily in a pocket or bag.

The JUMP is available in two versions: Lightning (for newer iOS devices) and micro-USB (for Android and BlackBerry devices, or anything else using that type of connector). The early-bird backer rewards already gone, but you can still get a JUMP charger at the $40 tier.