Daniel in SD
(supervised)
The homeless people in San Diego all seem to have smartphones. 81% of Americans have smartphones.The most populous state of the union is California. 48% of the known cases are from Hispanic patients. A significant number use prepaid phones with no web apps. It might work, or it might not.
As far as the Luddites like myself: I know I'm not loading somebody's random malware on my phones. The government databases have been breached by outsiders, insiders, and from legislation. They are already considering to have the "COVID app" to help voter registration drives by the DNC. Two birds with one stone. The stone is paid for out of our paychecks.
And it would not work with people like me anyhow. I have 5 portable phones I use, and only two have apps. When I'm out having fun, I don't carry one.
You could use a separate prepaid smartphone to run the app if you're super paranoid. Anyway, it doesn't have to work for people like you, most people run many privacy invading apps on their smartphones.
P.S. I'm always surprised that luddites own Teslas, the most privacy invading conveyance ever built.