OK everyone, walk back from that ledge. Someone with the resources and motiviation to drug/kidnap/kill/amputate to get access to a biometric scan is going to be well-equipped just to steal the device and read the flash out via JTAG.
Screen locks do not provide meaningful security vs. a determined attacker, and never will no matter what the unlock mechanism is. Unless you encrypt all storage with a strong password (not a 6-digit PIN) and a good PBKDF, all you get from this stuff is protection against casual snooping.
Or it's just the cops, and unlike a password or pin or pattern, they can actually physically force your authentication out of you with a single finger press.
Theoretically you can do some liveness checks (work better on retina/iris than on fingerprint), but basically everything related to fingerprints is easy to forge outright, let alone making a dead man's finger appear live.
Every time fingerprint scanners are mentioned, people start talking about cutting off fingers. Guess what: the people making the scanners have considered this scenario. All of their clients have nagged them about it continously for decades. It's fun to talk about, but it won't work.
