I am working on an application that will keep an eye on specific folders on a computer and monitor whether a modification will occur, I am wanting the capability to monitor Windows OS, OS X, Linux. I am planning on developing this in python, from what I have been able to find it seems watchdog library is the way to go (link below) does anyone have any experience with this? Any tips? (Suggestions in other languages would be great as well!)

https://github.com/gorakhargosh/watchdog

For Unix/Linux systems (that should include OSX), you would use the inotify tools and api's. I don't know what the equivalent would be on Windoze systems. You need to do some searching in the MSDN documentation or Google it.

FWIW, I have a fair amount of experience with inotify on a variety of systems.