I would like to implement the following thing: write a daemon, that will listen to method calls and turn on certain activity on demand. The problem is, that this activity should be turned off, if no application requires it (all the listeners exited).

Is there any standard way to do this (i.e. to make daemon aware of the applications listening)? Or is it DBus just broadcast, so the listeners should pass their PID so I can check if they are still running?