If a corset seems too much like a regular piece of clothing try a rope corset. Twisted Monk shows how to tie one on:
http://youtube.com/watch?v=vnY-ZFao7nk&feature=related
Also, if the subbie is wearing long pants and sleeves, a set of rope cuffs might be fun. They can be nice and firmly tied but still not enough to cut off circulation. They would be felt as the arms and legs move and with the right kind of rope can leave some quite attractive rope marks when removed. (I love rope marks)