[mythtv] Displaying messages from mythshutdown in mythfrontend - ideas?

[Matthew Wire]

A simple use case:

mythshutdown -x returns false, can't shutdown system.  I want to inform
the user via a dialog that it ran successfully.

For example, such a dialog might appear:

/--------------------------------------\
|Cannot shutdown at the moment because |
|     "My program" is recording.       |
|                                      |
|                 [ ok ]               |
|     [ Override and shutdown anyway ] |
\--------------------------------------/

(Ignore the wording etc, basically such a dialog would need to have
configurable text, and configurable buttons).

Clearly, there would be many other uses for this kind of function as
well.  I could display a message to the user while watching tv via
mythtvosd but this is not interactive and furthermore only works in tv.

1. There needs to be a way for external programs to inject messages into
mythfrontend.
2. mythfrontend needs to interpret these correctly.
3. Two-way communication may be useful (eg. mythfrontend says to
mythshutdown - force shutdown anyway).
Maybe the network control interface could be used?

Not looking for a solution on a plate but some ideas to help me go about
this.