Hello!
Okay then. It turns out that Parallax, a company who makes a family of excellent microcontrollers, does make a good sized battery pack. It does not where a protective circuit like the one that you are thinking, That's this thing, http://www.parallax.com/product/28989 it also has an onboard charge function.
As is this one, http://www.parallax.com/product/28988 for what I might be planning, I figure I'll adapt that one. For demonstrations, it would be the first. As for your power shutdown circuit, it shouldn't be too hard......