ZUPS allows for monitoring the state of one or more UPS devices using SNMP and executing user-specified commands in case of power outage, such as email notifications and controlled remote host shutdowns. If the UPS devices are running on battery, the shutdown commands are executed for an arbitrary number of remote hosts, optionally with some delay specified for each host. ZUPS can be configured to ignore these delays and run the specified commands immediately if the UPS devices are running out of battery power. Custom plugins can easily be added in order to perform other checks.
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.
PowerTop is tool that detects which Linux programs and kernel tunables are resulting in the largest power consumption and use of battery time. By fixing (or closing) these applications or processes, you can immediately see the power savings in the tool. You'll also see the estimated time left for battery power if you are running a laptop.