A command line tool (daemon) for OS X that monitors sleep, wakeup and idleness of a Mac. It can be used to execute a Unix command when the Mac or the display of the Mac goes to sleep mode or wakes up, after a given time without user interaction or when the user resumes activity after a break or when the power supply of a Mac notebook is attached or detached.
A little bit knowledge of the Unix command line is required to benefit from this app.