I wouldn't keep anything that sensitive on my phone that I would need to worry about 5th Amendment issues. Really if you are that worried about it, either don't keep it on your device or use some third party encryption with an insanely long pass phrase, that you don't write down anywhere.
I find that the fingerprint reader is on par with the facial recognition unlock that many devices have already. I wouldn't consider this "ironclad" security, but it is useful for things like keeping a child out of your phone etc. I turn on the facial unlock when I would be over at my brother's house. My nephew loves anything electronic (he even bought a game through XBOX live).
12 Pubs, 12 Pints, what could possibly go wrong?
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