Apple has released their launchd process manager under the Apache Open Source License (version 2.0)
Launchd combines most of the features of the venerable Unix cron and init facilities. You can use launchd to make sure a process is always running ("watchdogging"), to run jobs at specific times, to run jobs when/if a file appars in a specified directory, etc.
I cover the basics of launchd in my book, "Unix for Mac OS X Tiger", and ars technicha covers it in their Tiger review.
There is already a FreeBSD port of launchd.
Macscripter.net has an article describing how to use launchd with AppleScript to access a Flashdrive.