That would be a terrible idea. I mean seriously terrible. Although biometric authentication sounds good at first, on a personal level it's good enough and if you're physically present it's very hard to manipulate, still, there's a huge problem with that. It cannot be replaced when compromised. When (not if) someone gets hold of your fingerprints, iris and retina scans and voice profiles, they can use it to impersonate you online and you're left with no options. You can't change the skin on your fingers, your eyes and your vocal cords.
We leave our fingerprints literally everywhere we go, moreover most smartphones have fingerprint sensors nowadays, and every device with a microphone can (and often will) record our voices without our knowledge. These two are already unsafe methods of authentication unless we are physically present and we're getting to the point where our smartphones have front facing cameras good enough to at least partially take a picture of our eyes, some already use it to unlock the lock screen. Iris scans are already here and in a few years retina scans arrive to consumer electronics and from that point onward it will be as useless as fingerprints and voiceprints are today. I mean not useless to lock your phone but useless to authenticate yourself digitally.
The safest method is an NFC chip with a huge amount of randomly generated data. It would be unique to everybody and when it gets compromised, the authentication can be disabled and you can get a replacement. And it would be very cheap, much cheaper than biometric scanners. You could also have more of them, each with a different purpose.