Apple aims to ditch iPhone passcodes

"For example, a thief sitting on a bus may notice the four characters
that an unsuspecting person entered on the person's smart phone. As another
example, a thief may pick up a tablet computer in a public place and
discover, based on finger prints on the display of the [...]
Source:
http://www.ezonearticle.com/2013/02/10/apple-aims-to-ditch-iphone-passcodes/