The Scosche FlipCharge Burst ($49.99 direct) is a portable battery for your iPhone or iPod that can help you get a small charge when you're in a pinch. However, it's a little expensive for the limited juice it can provide.

The Burst is a small, pocket-friendly device, measuring 2.31 by 1.75 by 0.49 inches (HWD) and weighing in at just 1.2 ounces. You get a built-in carabiner, which makes it slightly larger on one side, but still very portable—plus it adds the ability to clip on to bags, key rings, or anything else you can think of. True to its name, the FlipCharge Burst has a 30-pin Apple docking connector that flips easily in and out. It charges via an integrated USB cable that handily stows away in a magnetic notch inside the Burst. This USB cable also allows you to charge and sync your iPhone or iPod. It's a nice touch, since carrying around an extra cable can be a pain. 

Four blue LED lights indicate the level of charge. A button on the side of the Burst activates the LEDs, but, oddly, the lights are very bright, and I found myself turning the Burst over to conceal them. There's a 720mAh battery inside.

In my tests with the iPhone 4S, the Burst added just 3 hours, 17 minutes of continuous 3G talk time. But the FlipCharge Burst isn't meant to be used as an everyday power solution, but rather as an emergency source to give you a little more juice when you're in a pinch. The similarly portable Mophie Juice Pack Reserve ($34.95, 3 stars), with its 700mAh battery, added 3 hours, 33 minutes, which is a negligible increase over the Scosche. The Juice Pack Reserve has a better design and costs $15 less, but you give up pass through charging and syncing.

If you want a more comprehensive power solution, check out some iPhone battery cases, like our Editors' Choice Mophie Juice Pack Plus ($99, 4 stars), which added an impressive 10 hours, 43 minutes of talk time to the iPhone 4S. Though it only adds limited battery life and isn't cheap for its capacity, the Burst is a nice, portable companion that can easily be clipped to a bag or belt loop so it's close at hand in case of a mobile power emergency.