Buy pointing a gun at the owner?
To add some context, Argentina has a history of robbers asking people to do complex tasks at gun point, like withdrawing money, and other things during “secuestro express”.
Lots of people keep talking about password codes, etc. You should be able to hand over your phone to an attacker and walk away knowing you and your data is safe.
At least don't use biometrics, they will cut off your thumb AND steal your iphone.