Recently I mentioned about possibility to control X10 devices from MythTV interface. Here is a detailed explanation how to add that feature into your media center. As I suspected that approach uses Perl interface to the X10 API (ControlX10-CM17). It also needs libdevice-serialpor.
Using approach showed below you’ll able to control X10 devices not only from MythTV on-screen menu but from its remote control as well. Great work!