Multiple bluetooth audio devices iPhone

I was wondering if the iPhone is able to transmit audio to multiple bluetooth devices at the same time. I have two bluetooth headphones and sometimes two of us want to watch the same thing on the iPhone or listen to the same music, is it possible if we purchased another bluetooth headphones can both sets of headphones listen to the music on the same iPhone or can it only transmit to one set of headphones?
iMac Mac OS X (10.6.6)