it's a relatively new invention. made of food-grade silicon i believe, it's like a little egg cup which you insert and it catches any discharge. it does need to be emptied, so i too am curious as to how it would work in a public loo - you wouldn't want to be rinsing it in a handbasin, and i guess it would be quite a messy job all round.
my 29 year old niece who lives a very green lifestyle, uses washable towels. they're the same shape and size as disposable ones, but made of toweling and some other material, but as far as i know, they don't have a waterproof membrane, so it's back to the leakage problem i would have thought.