I have a Samsung Galaxy Nexus GSM with the latest Google+ app installed.
I have an issue with Bluetooth headsets that are paired with my phone during a hangout. When I get a Hangout call, or if I initiate a hangout, I have never been able to have it so the audio plays through my Bluetooth headset. It just goes through the phones external speakers.
To confirm, my Bluetooth speakers work fine with Music, Movies, Games, Skype, etc.. It's just Hangouts that won't play the sound through the Bluetooth speakers/headset.It works if I plug headphones into my phone, just not wirelessly with bluetooth, which I find strange.