ITunes Match
I believe the is an icon next to each song in your itunes library to indicate that it is matched and in the cloud. however useful this is to confirm it has been successfully matched as it of course should be it is surely more important to flag an item that is actually on your device so that you know you can listen to it even if you have not wifi or 3G connection. How do you know it is on the device and not just in the cloud?