Putting a small device, the size of a key fob, in your pocket could "authenticate" your entire body for various purposes, such as unlocking your front door, or using a firearm. Those items wouldn't work for someone else...
https://www.neatorama.com/2013/03/10/Secure-Guns-and-Gadgets-with-Authentication-System/
Secure Guns and Gadgets with Authentication System
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