Don’t ever hand your phone to the cops
No matter what, teaching people they can add their IDs to their phones means some people will inevitably leave the house without physical ID, and that means creating the opportunity for cops to demand phones — which you should never, ever do.
Don't.
Ever.
This is among one of those many, many privacy stances most people do not understand. "I don't have anything to hide," they say. "Let the cops have my phone — I don't care." Or alternatively, "I don't care if Google tracks me — I don't have anything to hide."
Let's be honest — most people don't understand how a computer works, let alone how databases compiled by thousands of computers put together tracking profiles that know everything about them. They don't know how invasive it all is, how they're handing over their entire lives when they hand over their phones (or consent to tracking).