Search in the forum for "cloth". I once posted a link to an intel site with nice explanations of mass-spring-systems. A6 does not have those built-in but they are not terribly hard to write yourself.
i was thinkning in someting, like: is possible to attach bones to small mdl boxs, and then each box has an physic action, when the player touch a box, the box will move a bone, that is attached in MED in one vertix, and then maybe you can have a cloth , i don't know just a thought...
It's a pretty nice effect, though I don't know how they do it in games I've played. I can recall in Splinter Cell and Fatal Frame 2 some instances where you walk through curtains that react to the player.