Yes, it should be doable. I do a similar thing on my InputManagers folder. I forget where I got the idea from but the point is to catch any software installing any sort of Haxies in there and notifying me if it does.
You can do a similar thing. Add a rule like "Date added is after date last matched" to catch any new files/folders added and do a Growl notification (you need to install Growl for this to work, of course).