I've been trying out the ZAGGsparq 2.0, a ridulously simple battery charger for my iPad and iPhone. Although I rarely have a problem with the battery life for either of these devices, there are times when I could use a little extra juice, and I'm not near a plug or grounded power supply. That's where ZAGGsparq comes in handy.
Once it's fully charged (which takes about 9 hours), the ZAGGsparq can recharge your iPhone 4 times. The device has two USB plugs; the top one is optimized for a "power" charge, for devices that can handle an optimized charge. The bottom plug charges devices that do not utilize the optimized specification - it will still charge your iPhone or iPad, just not as fast.
I was in Toronto last week, and noticed while I was in the Immigration line that my iPhone battery was a little lower than I would have liked. I whipped out the ZAGGsparq, plugged it in, and 20 minutes later when I was through the line the iPhone was almost fully charged.
There are a couple of negatives to the ZAGGsparq, although I don't necessarily consider either a deal-breaker. The first is that a fully-charged ZAGGsparq won't completely recharge your iPad; it will only charge it up to 60%. This really shouldn't be a problem, because the main point of this device is to provide you with a little extra power until you can get to a power outlet. The other drawback is a bit more limiting - ZAGG says that if you are charging a device that draws a significant amount of power, like the iPad, you may not be able to charge your iPhone in the second outlet at the same time. In fact, if two high-power devices are connected, it may actually deactivate the ZAGGsparq.
Despite these limitations, I still recommend the ZAGGsparq as a battery-charging tool - it's relatively light at 8.6 ounces, and is pretty compact. You can get it for $99.95 at ZAGG.com, although I was able to get mine at my local Radio Shack. You can also find ZAGG products at Best Buy, Target, and Staples stores, among others.