There is a modern version of the wind weapon available called the Skimbat. See
http://www.skywings.fi/
I think the sail area is around 5 meters. I was considering buying one for snowboarding but decided to get a kite instead - mostly because I thought it wouldn't be powerful enough for the light winds we get where I live.
I'm kind of suprised that no one hs tried these skimbats out out on the water in high-wind places like the gorge or maui. If it works in the snow with a snowboard why wouldn't it work in the water with a wake board or a directional kiteboard?
I remember seeing color photos of a guy using a similar but heavier looking rig in an old windsurfing book (mid 80's?). I think the book said that the the problem was that it was too easy to get pulled off of the board - but the guy was on a gigantic long board with no straps.
A smaller board with straps or bindings should solve that problem.
Andrew if you windsurf you should talk your friend in to getting one of these things and then borrow it to try out on the water and report the results here.