I have a macbook pro with minidisplayport (MDP) out. It's plugged into an external monitor. Sometimes via MDP-to-DualDVI, and sometimes directly via MDP. I'd like to extract the digital audio signal from the MDP connection. I've seen cables that go from MDP to DVI+Audio. I want a cable that goes from MDP to MDP+Audio so that I can feed the audio into something other than my Apple Cinema display (which has cruddy speakers).
Since I don´t assume anyone to ever build a mini DisplayPort to miniDisplayPort+Audio Adapter, and the option of going mini-DP<>Dual DVI<>mini-DP seems to be quite expensive and bulky, why don´t you simply use the optical audio from your MacBook Pro´s audio output?