I was thinking of something like a finger scanner (note I did not say fingerPRINT scanner), where you would press your index or thumb on a selected area of the screen. Instead of scanning your fingerprint (which is impossible for the touch), it could check if the size of your finger matched the size that was previously stored as the correct finger size. Thus we would have a finger scanner that could be used to unlock apps (using mobilesubstrate) or unlock the lockscreen. It wouldn't be as secure as a real fingerprint scanner, but it would work as long as people had different sized fingers. Any ideas?