Basically, you just put in your body weight and it recommends the ideal kite sizes for various windspeeds. For the boards you put in your body weight and it recommends the sizes for beginner, light wind, medium wind, and high wind twintips. I haven't put surfboards, skimboards, or raceboards into it.
It probably won't be very useful for good kiters who already know what stuff they need for what conditions, but I think it might be helpful for folks who are just starting out, especially if they are lighter or heavier than usual and need to make sure they get stuff that is proportional to themselves.
Agree on the kites but boards are way off unless you're riding bindings. At 82kg's its suggesting a 149 for moderately powered when in reality a 133 would be better. High powered would be a 130 and light wind I could easily get away with a 140x45.
Ya, I almost wasn't even going to try a board size calculator since it's such a subjective thing and it's unclear how the dimensions should scale with body weight, but I went ahead and did it. Basically, I started with what I would ride at my 160 lbs weight and then made the length and width dimensions of that proportional to the square root of body weight. I'm going to tweak both the initial sizes and the scaling factor to see if I can make it a little more realistic.
UPDATE- Just tweaked the scaling factor to be the cube root of body weight instead of the square root of body weight so its less sensitive to body weight. Also tweaked the base values a bit so for a 160 lb rider it recommends:
Beginner Board / Easy Cruiser - 170 x 45, narrower at the tips, moderate rocker and flex
Light Wind Efficiency Board - 150 x 45, rectangular, flat rocker, fairly stiff
Board for Moderately Powered Riding - 140 x 41
Board for High Powered Riding - 128 x 38