If you've owned an Apple iPhone 3GS, 3G or still have an original iPhone, I don't need to tell you that one of the constant hassles with the phone is battery life. It's better in the newest phone, but everyone who has an iPhone seems to have their own strategy for minimizing battery usage, ranging from "don't use the 3G network" to "disable wifi" to "turn off everything, especially bluetooth".

I leave everything enabled on my phone except Bluetooth and my adaptation strategy has been to have lots of power cords with me: two in my house, one in my car, and one in my computer bag so I can sip at USB power whenever I'm using my computer on the go. It's a hassle, but it's manageable.

Where this breaks down is when you're at a trade show or out for the day, without the chance of getting near a power plug, computer or vehicle. You've seen it at parties, i bet: people making BFF's because they have the ability to quick charge iPhones, huddled by the wall outlet like it's the illicit drug of choice.

It's no surprise that add-on and extension batteries are a popular accessory for Apple iPhones, and six months ago, the major contenders were awkward battery devices with universal plugs that acted like an external gas tank: useful if needed, but clunky as heck.

The newest generation of these devices are sleek and double as iPhone cases, and two of the best are from Tekkeon and Mophie.

Do they work, though, and how do they compare? Read on...