The gadget ziggi posted just uses the wiring to send a different signal across it ( bit like the broadband across the mains idea)
If it's a PC display you're sending s-video's no good and it's a VGA splitter you want.
So, you want something like these
http://www.42u.com/video_splitters.htm http://www.digitaltigers.com/sidecar.shtml Got any old PC's kicking around? Use this
http://www.maxivista.com/