ironman,
This is not a complete answer, but maybe some of the other users here can help flesh it out a bit.
From my experience, X10's VA11A can be seen by Windows Live Messenger as a web cam. I'm not positive if that still holds true with the latest model number VA12A.
The VA's will take standard NTSC video and raw audio as input.
Since you already have a X10 wireless color camera, you probably already have a X10 video receiver. That would receive the wireless video from the camera, and when connected to a VA and then to the computer, you have video. The audio may be more difficult, depending on which camera you have and whether it has a built-in microphone.
Also, the X10 wireless cameras are not truely wireless unless you buy their add-on base that houses batteries.
I will finish by saying that at least one member here has used a cheap 1.2 GHz wireless battery powered camera, made by another manufacturer, successfully for video, at least.
Any thoughts guys?