Heh. I was offered one at a local store. Looked neat, even smaller than the one in the OP. Has an option to use one or two batteries (requires screwing on an additional section). Price wasn't murder, eiher, so I became intruiged. Well, I gave the clerk the back-up AA I carry in my jeans change pocket (which I had tested prior, seeing how it's for *back-up*) and asked her to charge my phone. Apparently, my battery is "faulty". Naturally, I "bugged out" immediately and made sure to re-check the battery afterwards.
Hope yours works better.