So far I have written an X10 server that runs as a Windows service (so it automatically starts when my machine starts). This server keeps a live connection with the CM11 module (using the COM1 port) and it makes its services available through JMX.
I have also started working on an Eclipse RCP client application. The client starts minimized in the system tray and through a popup menu you can send commands to the server (using JMX).
Of course there are still many things to do: logging, supporting macros that combine multiple commands, supporting scheduling of command/macro execution, I18N and L10N and so on.
I'm also considering opensourcing the whole thing. I'm still struggling a little bit with the legal issues though. The third party library that sends the X10 across the wire is GPL and it requires an older version of the Java Communications API (2.0) which is no longer available for download. Both licenses need some further reading/studying before I make the jump.
Interesting times ahead...