https://www.macrumors.com/2017/08/17/ios-11-emergency-sos-di...
> In iOS 11, Apple has added an "Emergency SOS" feature that's designed to give users a quick and easy way to summon emergency services should the need arise. As it turns out, there's a secondary benefit to Emergency SOS - it's also a way to quickly and discreetly disable Touch ID. ... This is a handy hidden feature because it allows Touch ID to be disabled discreetly in situations where someone might be able to force a phone to be unlocked with a fingerprint, such as a robbery or an arrest. With Touch ID disabled in this way, there is no way to physically unlock an iPhone with a finger without the device's passcode.
What does that mean? It calls 911 or the local equivalent? That doesn't seem like desired behavior if you're triggering it in anticipation of crossing a border.
I'd say it's better security practice to only use a passcode and, if you must use any biometrics, use an obscure finger (like the side of your pinky finger or something) - whilst also enabling the the auto-wipe feature after 10 failed login attempts.
IANAL but from what I understand of the current goings on in the states, the police have to tell you which digit to try. Just as a password is protected, knowledge of which digit and how it should be placed is also - technically - protected. Think of it like two-factor authentication: The fingerprint is what you are, which was can be used to unlock the phone, but divulging the "which finger and how it should be placed" is what you know.
I can't seem to find it but people were "hacking" the biometrics of Androids with 3D printed heads. The trade-off of convenience for security isn't really worth it.
Again, IANAL, and IMHO, and - if you care about privacy - you shouldn't use biometrics whatsoever but I understand the trade-offs between convenience and security and why so many people fall into that trap.
Waiting for a case where the FBI bangs down Google's door to get access to a locked Android phone before I make any assumptions about the security implications of that though.