D-bus is a simple way for desktop applications and system services to talk to one another and coordinate process lifecycles. D-Bus messaging system has been adopted by GNOME, KDE, Xfce, and systemd.
Dave Collins gave a live demonstration. He monitored d-bus messages from rhythmbox with d-feet. He identified the messages for soundtracks and incorporated the found methods in his custom python application.
A graphical utility for analyzing d-bus methods and signals.