You mean flipping a laptop lid open and using your face to log in?  PIM theoretically supports it, but you'd have to have a gnome frontend and a recognition module, which is probably quite difficult to make.  I look forward to seeing it happen though, however long it takes.  That is after all one of the three main reasons for having a  built in webcam..You could mean something completely different though, I don't know- I'm confused.  It does not appear that english is your first language.