I bought one of these a couple months back. It's a good deal at $30. And yes, it can be used to charge your smartphone or iPod or iPad.
You still need the official charging cable and power brick to charge this external battery, as opposed to something like the zaggsparq 2.0 (can be bought for $50 during zagg's frequent sales), which can be plugged directly into the wall when you want to charge it.
Conversely, I feel this Sony battery holds charge longer than the zaggsparq 2.0 will when you are not using it. This may be because it has an actual power button that you need to turn on when you are delivering juice to your vita or other device. It has a slightly smaller capacity than the zaggsparq 2.0.
It's small enough to fit in your pocket. The power button on the device has three or four colored LEDs. Green, orange, yellow and red I think, which let you know how much charge the battery has left.
Anyway, for $30, it's a no-brainer. I'm gonna go buy an extra two for my phone and iPad.