>>8948>Are commercially available fingerprint sensors a fake?
Lets say it's a very low security hurdle.
The biggest flaw is that you can't change your finger-print, so if somebody has managed to lift your finger print from a surface you touched, the security is broken and you can't reset it. There are already black markets for finger print databases. Some smartphones scan your face instead of your finger, you can't change your face either.
You can get a special usb-stick that plugs into the charging port of your smartphone to unlock it. That's very safe if you can hold on to the usb-stick.