On DBUS

From http://www.freedesktop.org/wiki/Software/dbus

D-BUS is a message bus system, a simple way for applications to talk to one another.

And now, thanks to iXce, they can talk to Compiz too.

http://www.compiz.net/viewtopic.php?id=1173

Gives the details of what he has done.

There are now patches to allow calling of methods from

• Cube (from iXce, original post)
• Scale (PlayerX, here, and an update here)
  
• More Cube (PlayerX) here
  
• Water (PlayerX) here
  
• One to activate a window: here (PlayerX again!)
• And finally one for replace by iXce:
  

There are other patches in that thread, it is best you read it to get their context and purpose

See the wiki for a dbus howto: