I found this tool in the process of trying to do something similar to what you want to:
This lets you monitor the qcop channels System, Taskbar, Network, Card, and Sync, and log their events to a file. You can also specify a "user channel" that would let you monitor the messages sent to an application of your choice. . . Personally, I haven't had much luck getting it to work- I'm trying to figure out qcop messages for the PIM apps.
If you figure out how to get this to work, or another clever way to find qcop messages for a particular app, by all means let me know.