okay, 1.3.0 is done.
now you can run a custom command. note that it will be run as 'user' not 'root', and please let me know if it's not working in some situations. I didn't test it much.
It will run the custom command once when a rule becomes true, and then again later if the rule becomes false and then true again. If anyone wants to explain why this isn't good enough, maybe I can add some more options...