I use a rather spartan windowing manager called awesome in all of my machines. This has been a fine setup until I used it on my netbook due to one small issue, battery monitors.
On my desktop machines and the laptop I use gkrellm to monitor cpu and memory and for the laptop it has a handy battery usage label. With the netbook however, screen real estate is quite valuable, so I opted for finding something to sit in the system tray.
After a quick look it seems there was nothing which was lightweight or simple or not requiring me to install the entirety of gnome.
In the end I made my own called rbatmon, then packaged it up for use in the AUR. If you have a substandard flavour of linux, not to worry, You can grab the script from my githib page here.
The most interesting challenge of this was building a package for the first time. There is a great package for Archlinux called abs (available on pacman) which fills /usr/share/pacman with some example PKGBUILDS for standard sources of gettings code from VCS’s.
Page on my site regarding this is here.
AUR page is here.