I have two computers testing cooker stuff. I share a monitor and keyboard between them. I can't share the mouse, cause when X loses the mouse, well you know.
I would figure that XFree86.org would be the best place, but maybe someone knows a trick. Think asking XFree86.org to work on this would produce any results or would just be a waste of time? Again, hate to say it, but you can do this in Windows, but Windows works differently. I would think it wouldn't be that hard to do, the keyboard is shared and it doesn't have a problem switching between the two.