I was thinking the other day how cool it would be to have a minimal X server, hooked up to my TV with some sort of chroma-key overlay.

So, if the X server had nothing to display, the normal TV came right through, but if a window were opened, it would display the window.

Does this sort of a device exist? Has someone rolled their own?

Basically I just want a small box, with a network connection to sit between the VCR and TV to give a nice clean interface to the home automation system I'm putting together.