I was browsing the mailing list and noticed an interesting patch that may or may not be of assistance for getting the navigation and other buttons working in MythTV.http://svn.mythtv.org/trac/ticket/757
I also have found the following plugin that sounds like it may be trying to do the same thing that Pluto is try to do, ie communicate with Myth. According to the website,
The plugin opens a socket (on the fontend) that listens for incoming messages. The messages are being interpreted by a free protocol (it is stored in the database). Next, an according keyEvent is sent to the application.
Communication in both directions is possible.
A sequence diagram can be found here.
The screen sequence in the webinterface can be seen here.
Here is the link: http://studwww.ugent.be/~aveys/mythwifi/
I am not a programmer so I do not know how to proceed, but it does sound interesting.