What about PHONE PAIRING, where you link your iPhone to a laptop and only the laptop can be used to image the device?
This is typically used by organisations managing IT assets.
If crossing a border, guards would normally take the phone off you, rip off all your data/passwords etc, then hand it back. This would mean that they can't do that, and you can't unlock it for them, so they might have to be more straightforward and take the phone away from you, leaving you pretty screwed and maybe have to fly straight back home in many cases I'd imagine.