Thes could just be snap-on without the need to plug a connector to t5he micro-usb slot. That way we would get an external battery and better protection - perfect for prolonged outdoor use.
If these power packs would feature a micro-usb connector so that they could be charged on their own, you could buy multiple of these jackets and just change trhem if the power runs low.
I imagine they could be built very cheap by some chinese manufacures - not much more expensive than a chinese replacement-battery.
I would especially like to have a camera tripod thread in the case as well.
What do you think?