D-Bus: is there such a thing as a "D-Bus sniffer"?
Bustle ( http://willthompson.co.uk/bustle/ ) will help you visualise the flow of messages over the bus. This uses the same basic mechanism as dbus-monitor to monitor the traffic.
From the website:
"Bustle draws sequence diagrams of D-Bus activity, showing signal emissions, method calls and their corresponding returns, with timestamps for each individual event and the duration of each method call. This can help you check for unwanted D-Bus traffic, and pinpoint why your D-Bus-based application isn't performing as well as you like. It also provides statistics like signal frequencies and average method call times."