After some research I found the 'HFP for Linux' project.
- Check out the sources:
svn co https://nohands.svn.sourceforge.net/svnroot/nohands/trunk
- cd into the source directory, then compile and install the software. I had to install the packages automake, libtool, libbluetooth-dev, libasound2-dev and libspeexdsp-dev before.
sudo make install
- Make phone bluetooth discoverable. Somewhere in your phone's settings
- search devices
- Configure audio to OSS /dev/dsp
- launcher use /usr/local/share/hfconsole/icon.png