In reply to Michael Hood:
I absolutely love the fingerprint scanner on my phone. But as said above it can't read if your hands are damp.
With the location of my scanner I find the thumb and middle finger on both hands are best, as these naturally fall in the right position so the phone just unlocks itself when I pick it up.
My husband has a manual job and finds them useless, so sticks with a Pin code. I know many climbers who also have difficulties with fingerprint scanners, so they are handy but not perfect.