My apologies if this stuff is covered above. It’s late and I didn’t take time to read the entire thread.
There is no need for an implant, which BTW is not even properly classified under the topic of biometrics, IMHO.
Biometrics are the parameters of YOU. Your facial structure, your body shape, your gait, your fingerprints, the patterns of veins on the back of your hand or on your retina. No matter where you go, you take all those things with you.
We now have cameras which can scan your fingertips for fingerprint patterns from a distance of some feet, meaning you will never know if they don’t want you to.
The combination of computing and high-resolution cameras leaves little opportunity to be a stranger to the system.
Ironically enough, the only way to have a physical presence in a public place while not revealing your identity will be to use a generic robotic avatar, with all comms encrypted and/or anonymized.
Or wear a hijab and put rocks in your shoes to disrupt your gait.
Privacy will increasingly become infeasible for all but the very rich, and those who are so deprived that they’ve never interacted with the system.
Well put,all kidding aside.