I did some research on this topic:

the Headset ("audio sink") profile can be activated on the N900 using

However, you can't connect to it from your laptop, because the phone doesn't know what to do with the connection

So here is an approach to forward the data to the ESD sound system: http://talk.maemo.org/showthread.php...ighlight=a2snk

But the N900 uses the PulseAudio sound system, which should implement this functionality itself (see http://www.pulseaudio.org/wiki/Modules#Bluetooth). This documentation seems to be outdated, because PulseAudio on the N900 already has both, the bluetooth source+sink functionality (see pulseaudio --dump-modules | grep blue on the device)
I did not work out (yet) how to use is… Any hints are welcome

The ESD approach could also work, as the PulseAudio server has an ESD compatibility layer. But of course it would be nicer without this…

PS: to those of you not taking this thread seriously, shame on you
But really, I can imagine situations where I don't have a headset and I don't want to use the speakers of my laptop (e.g. in a train). Now, a solution to this thread would come in handy