you can implement the bluetooth profile for this (A2DP), the big issue here is not the music streaming but the roles, you iPhones are going to play, for instance, you can be a "sound-source" and transfer audio to a "sound-sink" device, those roles have to be previously defined on the handshake and paring action, furthermore, if you are able to browse the properties of an iPhone you will get what port and what roles are supported, sadly muss I said, there is no sink role supported jet for iPhones, so the most that you can get till now is stream audio from iPhone to another bt capable device (speakers, pc, headset unit, etc) more info can be reached on the official bluetooth web site and what iOS until now supports.