@lapis
The general consensus is that biometrics (fingerprints, face readers, etc.) are great identifiers and terrible passwords. The most basic issue with using a fingerprint as a password is: what do you do when someone gets your fingerprint?
Here's one article about it: http://blog.dustinkirkland.com/2013/10/fingerprints-are-user-names-not.html
@mikeburns That is a really good point! Thank you so much!