BreakBox

Public secret code....
You want a code or an instruction public available, but only in case of an emergency.
Here the code is written on paper and there are 3D printed around it. You can now clearly see when some one have assessed the code.
Give a friend your house, garage or boutique key and the sealed alarm code and he can only enters the place when he have broken the seal.
You could even seal a key in a 3D print.

Ohhh yes... You can use it for the next Grammy show ;-)