When I leave #home, stop playing #iTunes.
If you're on a Mac, it's quite simple to get this working with Folder Actions (make sure they're enabled first) and Automator. Create a designated folder in DropBox called "music_stop" for example. Open up Automator and create a new Folder Action. Assign the action to the "music_stop" folder you made in DropBox. In the Automator library, search for the "Pause iTunes" action and drag it in. Save it. That's it. IFTTT and DropBox will take care of the rest. The same can be done for playing iTunes when coming home. I made one of those recipes as well. You can even set up some actions in Automator to shuffle your iTunes library.