acpid 1.0.6-9ubuntu4 (amd64 binary) in ubuntu intrepid

 Modern computers support the Advanced Configuration and Power Interface (ACPI)
 to allow intelligent power management on your system and to query battery and
 configuration status.
 .
 ACPID is a completely flexible, totally extensible daemon for delivering
 ACPI events. It listens on a file (/proc/acpi/event) and when an event
 occurs, executes programs to handle the event. The programs it executes
 are configured through a set of configuration files, which can be
 dropped into place by packages or by the admin.