Hi,
just want to note there's a cron-like daemon that allows to initiate actions not based on time but on filesystem activities. (File created, accessed, written to, moved, deleted, ...)
It's called incron because of it's inotify based nature. It's available at least for linux in the distribution repositories for quite some time now.
See the github page for some simple examples. (Search google for github and incron to get to the incron repository)
greetz,
architect