Power Monitoring Tools in Ubuntu 9.04
Heh, the power and energy monitoring tool (pwrkap) that I wrote last year has been accepted into Ubuntu 9.04. You'll need some sort of power supply that reports power and energy, such as IBM Active Energy Manager, or a post-2000 laptop running on battery.
http://packages.ubuntu.com/search?keywords=pwrkap
http://packages.ubuntu.com/search?keywords=pwrkap