This suggestion comes up in every single thread. Consider that when such an obvious gambit seems to exist you're almost certainly not the first person to have come up with it, and there's a reason it hasn't already taken off.
Care to share the reason it hasn't taken off? Or are you here just to call me out?
Other commenters on my comment have not provided a good reason. Like I said, I walk through customs and passport control with my phone in my hand all the time (20 or so trips per year) and could easily click this button the instant something unusual happens.