FluxBat is an ACPI based battery monitor for the fluxbox window manager. It includes two parts: a daemon process that runs the update script and the update script itself. The whole software contains only about 100 lines of code and is easy to use by including only one line in the menu configuration file of fluxbox.
asapm is an AfterStep look & feel Advanced Power Management (APM) monitor for laptop and notebook PCs running Linux or FreeBSD/NetBSD/OpenBSD and X Windows. It displays charge left in the battery, the time left to the total discharge of the battery, computer is connected to the mains or is working on a battery and the battery status high/low/critical.
wmmge is a little dockapp for Window Maker which monitors an MGE UPS. It shows the remaining time, and it blinks if this time is short. It uses PSP (Personal Solution-Pac) monitor, which can be downloaded from the MGE website: http://www.mgeups.com. It needs root permissions to send messages to the UPS.