Can you clarify what you're trying to do? Is the source the iPhone and are you intending to use the iMac's speakers?
Currently my iMac is connected to a set of speakers via the headphone jack.
Every now and then I'd like to be able to listen to podcasts that I've downloaded onto my iPhone with the iCatcher! app in my room.
However, instead of using the iPhone's small speakers, I'd like to be able to use the speakers connected to the iMac.
I know I can disconnect/connect the speakers directly to the iPhone every time I want to listen to something but if I could connect to them wirelessly, that would be great.