I think I would be able to do this by modifying iTunes’ launch services. Any idea how to go about that?
Would editing its info.plist file in a manner similar to below do what I’m looking for?
EDIT2: Last.fm’s official Mac Scrobbler (http://www.last.fm/download) is a perfect example of the functionality that I’m looking for.
The best way to do this is create an AppleScript that launches both applications, save that applescript as an application and use that to launch iTunes and GrowlTunes.
In Mac OS X, there is no (easy) functionality that detects application launches.
However, GrowlTunes is designed to be an always open menu extra application, and in fact has a way to launch iTunes from its menu extra. Why not just add it to your login items?