I don't know if this is new or not. But I came across this page and I thought you might find this interesting. I'm sure the battery experts here know more about this. http://www.electric-fuel.com/index.shtml
They seem to claim more time for cameras/cellphones/camcorders than the origional batteries. Of course the packs look as big as a wall wart A/C plug so it's obviously bigger than the battery that they would be helping, but is there something in how they work that gives them more run time.
I guess what I am getting at: is this just a cheap backup battery or something to look out for?
Or you could do what I did and make a battery pack with Lithium AA's to the right voltage of the device. Lithium's have a shelf life of 10 years and are much cheaper and lighter then zink air. If the device uses AA cells just carry the Lithium batteries