Finger print scanner for security 
Interested to see how this works. Was told last year by a security contractor that the reason these aren't everywhere is that they test super poorly. Said that they work 30% of the time when a person 24-50(or so) uses them and drops below 10% above that range.
Can you imagine 7 out of 10 times your phone doesn't work because it isn't reading your print right?
The guy told me that it was mostly due to inconsistency when presenting your print, and that is with building mounted scanners that don't move or rock in your hand when pressing your thumb.