Pandora System Info by Jon Sneyers is a ridiculously accurate battery information, so you can actually see exactly how fast the battery is (dis)charging and exactly how many micro Ampere hours it has left. Also contains a simple CPU usage monitor (including info on power-saving C-states), a simple SD card free space pie graph display, and network statistics.
Changes:
New in version 0.6: change your CPU and RAM clockspeed, toggle wifi and wifi power-saving from within Pandora System Info.