Not2savvy,
Sorry I have not replied until now, I had not noticed yours.
Im not too sure if OpenLP allows for messages to be sent across stage view or not, it would be a nice feature if it did. I will investigate.
You will probably find that most p.c's/graphic cards come with at least two video outputs, this would be the option I'd go for. If you do go down this route you may have the cabeling installed. If not, it might be a good idea to purchase enough to do two or three runs. You never know what your future requirements maybe.
Personally I shy away from any radio equipment possible. Use a wired connection where ever possible. Depending on the distance, cables are usually cheaper, provide better quality, are alot more reliable and you will suffer alot less noise issues. We have had lots problems. We have had guitars picking up the hearing loop, causing feedback. We gave up on a wireless video link to the nursery because it usually took 15 minutes every Sunday just to get a decent picture.
As for vga cables, I cant really recommend a particular brand. If your Matrix us similar to the ones I have been looking at, then they may well include a booster, which will do wonders for your video signal at the lengths you are talking about.
As Ronald said, you could use VGA to CAT baluns, bit be wary of cheaper versions. I have not had personal experience with these, but I hear they can be a false economy.
Phill