Putting aside the embedded beneath the skin aspect (I share your concerns), this concept can actually work - see FIDO2 and U2F protocols. They're actually pretty good from a privacy perspective too, and give you unlinkability between services (as the key you present is derived from factors including the verified origin, i.e. URL, of the resource you're authenticating to).
Clearly the verified URL origin of something in the real world is complex, but there are ways to potentially make this work. Devices might have certificates for a URI, and this URI could be verifiable and convey attributes like the GPS coordinates to within 25m, that you can verify before authenticating. Users could presumably also whitelist certain origins (garagedoor.home.mydomain.net)
All of this apart from the subdermal part actually could work out well - a small number of people already do this via U2F, or even traditional smartcards.
Clearly the verified URL origin of something in the real world is complex, but there are ways to potentially make this work. Devices might have certificates for a URI, and this URI could be verifiable and convey attributes like the GPS coordinates to within 25m, that you can verify before authenticating. Users could presumably also whitelist certain origins (garagedoor.home.mydomain.net)
All of this apart from the subdermal part actually could work out well - a small number of people already do this via U2F, or even traditional smartcards.