Notifications on Mac OS X I would like to receive a notification somehow when system events happen.  For example, a process writes to a directory, or a sandbox violation gets logged.  (Ideally when it occurs, the sandbox violation). 

Is this possible and if so how? Growl seems to work well for apps that already tell me things, but how about access of a directory?  Checksum change in tripwire? That sort of thing...
Growl comes with a commandline tool, 'growlnotify', that can send notifications. You can use that in scripts or from tripwire to send notifications to Growl.