Phone is basically vibrate mode 24/7 the Emergency Bypass toggle setting on each contact set, allows me to hear notifications for text or call for a select few while not allowing the rest. I’ve yet to see this feature on another phone. Just one of the things why I love iOS.
How does your phone know if they're calling because of an emergency? They might just be calling to say hi
Selected contacts with this toggle'd on when they call it'll simply ring overriding the silent/vibrate only mode.