For cryin’ out loud… Why in the world has someone not put a lipo, regulator and charger on a Arduino shield? You guys have all these things as stand-alone parts, you just need to stick them together. You got your single cell lipo (with a little step-up action for your 5v) which would be thin enough to be below the female headers on the sides. I am saying that this could be the first shield in your stack and it would not effect the original pin-out in any way allowing you to use all your other shields the way you always have. Stick a on-off switch on the side --why the hell does no one put a friggin’ on-off switch on anything? Charge the thing off of your USB. Done.