At
http://www.xgamestation.com/view_product.php?id=2 about a vector display
interface coming soon. Maybe emailing Andre will get you some information
about it.
You'll still have to design and build a doohickey to take an NTSC or VGA
input signal and convert it to a vector signal, if that's even feasible.
With the ZVG board that Tim pointed me to, it's a moot point fortunately.
I was hammering Google pretty hard and found a really cool site that shows
how to build a 'scope tube clock:
http://www.webx.dk/oz2cpu/clock-scope/scope.htm
..that in turn lead me here:
http://www.sphere.bc.ca/test/crts.html
So I'm a pretty happy geek right now. :)
g.