Turn Off the Music with the Phone

I've seen bluetooth connection between a cell phone and some new cars.  When the phone rings and if you are listening to the radio the radio shuts off/pauses play and the phone conversation can be conducted.  What if you could set up the same thing at home or in the office.  You could be cranking iTunes in your office while you do some monotonous work and when the boss calls you extension to ask you a question iTunes would know instantly to shut off.  You would have to connect your phone to your audio playing device somehow.  It could be nice for home as well where the TV volume went down when the phone rang for easier finding.