The new version of pulseaudio (0.9.22) has a dbus api that should give you this kind of notification. Unfortunetly, the dbus-protocol-module for pulse doesn't seem to be included in Ubuntu Lucid yet. I'm making a push for it to be included in MeeGo though. I'm having major headaches dealing with pulseaudio's c api right now, so i can definitely relate to some of the issues you are likely having.Three versions and still only an audio server stub...no access to volume change notifications. Last I saw, even gnome didn't have audio change notifications it just listened for the volume change keys and queried the audio server for the new volume.