It wasn’t long ago that TPOL was living in Shanghai (see TPOL in Shanghai). That seems like an eternity ago. One strategy the Chinese have developed to contain the outbreak is an app that, “Runs a continuous contagion threat assessment on you, then outputs it as a green, yellow or red QR code. Something that people (mostly in doorways) can easily scan” (see [How To]: Get Your Shanghai Color Code). In Shanghai, this code is not yet mandatory (see In Coronavirus Fight, China Gives Citizens a Color Code, With Red Flags). Beyond using the code to gain access to restaurants or bars, it is unclear how much access the police have to this data.
I leave the comments to you.