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.
upsguru is a daemon that monitors a UPS connected to a serial port. It has been extensively tested with a rebadged Centralion UPS. It communicates with init via the /dev/ initctl FIFO in order to control system services in the event of a power failure. The sample scripts include commands for SMS notification using gnokii. Protocol details are also contained in the archive.