I wanted an easy way of hooking workrave up with other programs.
I figured being able to call an external script was the easiest way
of accomplishing this.

This patch causes workrave to look for and run the script
~/.workrave/statechange using '/bin/sh'.  The script gets passed
two arguments: the first argument is the new state, the second is the prior
state.

What these mean can be found in /backend/src/ActivityMonitorInterface.hh.
At the moment, the important ones are State 2 (IDLE) and State 4 (ACTIVE).