Has anyone used something like this on their GoPro for extended power?

http://www.amazon.com/Jackery-Ultra-Compact-Aluminum-Portable-Rechargeable/dp/B00AA6CS86

I don't see why it wouldn't work, but want to see if anyone has given it a go.

There are all manner of these for sale.
I would carefully read the reviews to get a sense of its performance.
Be aware that many people give one-star ratings for the lamest of reasons,
so dig into the reviews to see how the product will really perform

I use one of the Anker batteries that's primarily for cell phones - they work fine and you can run the goPro for hours and hours on one.

Same here, Jim. I got an Anker charger for my iPhone, and in tests I did a 24 hour timelapse on my GoPro!

Now all I need to do is find a use for that....