The next new thing in mobile media is going to be "Ringbacks". Basically, when someone calls you instead of them hearing the phone ring normally, "brrrriiing, brrrinnng", they'll hear the song or recorded message you've set up.
Good business/techy overview here in Wireless: Buis and Tech. Says that ringbacks are much easier to deploy, because everythings done on the network. Also discusses how mobile media services, such as ringbacks can be bundled in the future.