Updated at 4:50 PDT: You can read the full review of the product here.
No matter how long your iPhone or iPod's battery life is, it's never long enough. (In the case of the iPhone 3G, it's not even long to begin with). So, it's natural that you'd want to get a juice pack, which will provide extended battery power that can double or even triple the amount of time you can use your device between charges.
Most juice packs work with only a particular model of a device. The Juice Pack Air from Mophie, for example, works only with the iPhone 3G.
This doesn't present a problem if you only have the iPhone 3G. But if you also have an iPod Nano, you may get frustrated with its inflexibility. This is when you want something like the iPWR SuperPack from Wireless Input, the first juice pack I've seen that works with most of Apple's handheld devices, including the original iPhone, the iPhone 3G, the iPod Touch (first and second generations), the iPod Video, the iPod Nano (third and fourth generations), and the iPod Classic. It's also one of the most affordable devices for extended battery life, costing less than $60.
Other than that, the iPWR SuperPack is equipped with an 1,800mAh battery to double the iPhone 3G's battery life. As the iPhone 3G is the biggest battery drainer on the list of supported devices, the SuperPack will likely increase use time even more for others, such as the iPod Nano.
The iPWR SuperPack does have a few easily noticeable shortcomings, however. For example, when connected to a device, it can't be charged, and you can't sync the device with a computer at the same time. It also doesn't have a battery gauge to show how much juice it has left.
Check back at CNET soon for a full review of the product. In the meantime, enjoy a quick slide show.