My friend Janet has a worthwhile proposal for a ladies' dating service. Make the guys send dirty tee-shirt. Guys are visual but for women it is all about pheremones, might as well cut to the chase. I guess there'll have to be some sort of disclaimer so the guy doesn't expect the tee-shirt to be returned laundered.
This strikes me as a pendant to the fabric-softener theory of territory-marking. I.e., no man thinks to use fabric softener on his own, so if he smells of the stuff that means he is taken.