Ok. I did not comprehend the word "work" very well. So the question was "How to set bluetooth as ALSA default output device" and not "How to get bluetooth headset usable by ALSA".
Originally Posted by slacktroll
... Setting up these device with blueman is not hard at all. ...
Neither is it hard on the command line.
sh /etc/rc.d/rc.messagebus start
sh /etc/rc.d/rc.buetooth start
hcitool cc BTMAC
hcitool auth BTMAC
Tested to work with SonyEricsson MW600. Your milage may very. I remember I got it from Gentoo wiki or Arch wiki (not sure) with a simple search on the Internet.