The device is called a "Minty Boost" after the tin is was initially designed around, a Altoids Mint Gum tin no bigger than the circuit and two AA batteries. With this you get 582mAh! You can also find mods to allow for a solar powered lipo battery version!
Rather than spend $40 for a largish, albeit sleek battery pack that does last 10000mAh, you can pick up this kit and tailor it to your whims. As you can see I currently have normal duracell batt's in it, which I needed to use up. For all my camera equipment I typically use these and plan to swap them out as soon as the duracell's wear out:
Initially I was going to use this kit in a dental floss container for super steath and a couple of AAA but the case was just too small.
I then switched to this altoids tin and was still using a 3 AAA holder with spares stored on the sides of the battery holder, but that didn't seem to give the same bang for the buck, so to speak.
I ended up with this current configuration though I'm thinking of using a three AA holder in place of the two AA holder.
Right now you can see the blue tack putty in the bottom holding the batteries in and somewhat insulating the wires from the bottom of the tin.
This is great for the ingress game from google. This kit offers up the viability of long sessions and the ability to customize or "hide" it to your liking for prying enemy eyes!
Hope you enjoyed this post and thanks for stopping by!