I think it's a great idea myself, but I don't see that going over in this country unless it is voluntary to be so registered if you test positive.
It’s only a great idea if it can be followed up by testing!
Why do I care if I come into contact with anyone who’s got Covid 19? I either get sick or not. I would know either way...
But if I live with someone immunocompromised, I would want to get tested every time I’m in close proximity of someone who is shedding virus, to see if I caught it and is shedding virus myself.
However, if I don’t get to be tested, what good does it do to know that I’m in close proximity of someone who’s sick? I can theoretically self-quarantine 14 days each and every time. But that gets super annoying. And probably not practical. Would my employer allow me to stay home each and every time I got an alert from my phone? I highly doubt it. On the other hand, if they don’t allow me to stay home, I could potentially infect my whole office worth of colleagues. Aren’t that nice?
So, without on demand testing every time I get an alert I’m in close proximity of someone infectious, I don’t see what good it does to know about it.
But if they say the phone alert is a passport for me to get tested, I’d be the first to sign up!
(You see where I’m going? Give me enough incentives, I’ll let you have my “private” information. Most of us willingly allow google to track us in exchange for navigating through traffic... But without such benefit, I’d be the first one screaming “privacy”!)