Also available from Amazon's AppStore, if you want to quickly see what your Fire's battery level is (including percentage charge) without having to go through the Quick Settings menu, you can try this app:
BatteryTime Lite
http://www.amazon.com/exec/obidos/tg...l/-/B004T555WA
While it's clearly designed for a cellphone, it provides the one bit of info I'm looking to see quickly: the percentage charge left in my Fire's battery.