AA batteries that charge in either a USB port or a standard NiMH charger are pretty much a great idea. When fully charged, these AA batteries last just as long as other rechargeable NiMH batteries. I normally get about a week out of them in my wireless mouse, then I?ll plug them into my USB ports on my Mac and in about 5 hours they are charged. If you want to speed up the process, just use them in any standard wall charger and you?re all set.
The covert USBCell is a great idea and works really well. The five hour charge on a USB port is long, but do it overnight, it will stop charging when it is full charged.
More USBCells are coming soon including AAA, 9V and Phone/Device batteries, so look out for them!