I work in the heart of a major metropolis (inside the top 50 US cities by population), so I know my phone has been within range of a victim, or a victim’s relative, or a person who has been in contact with a victim. The math simply says ‘yes’.
I have no need for yet another panic-inducement vector. See previous point, I do not see it as an ‘if’ but a ‘when’. And i’m okay with that.
I do like the innovative idea of utilising available resources and should imagine the software could be written quite quickly.
As far as signing up, I have very mixed feelings and would most likely sign up just to see what the interface was like and also the notifications which I am sure there will be many…
Similar to @m_hutley I live about half a kilometer from the Chinese Embassy in a densely populated area which caters mostly for Chinese, Koreans, Japanese and other SE-Asian nationalities.
I agree with @TechnoBear about “invasion of privacy” since it is proposed to insert the software into the operating system. I can’t ever imagine that once installed it will ever be removed. If the person that was recently diagnosed with the virus did not report because of having "other concerns’, no doubt the medical authorities would be very interested in accessing the records to find others who may be infected.
The software could easily be abused especially during lockdown when notifications about any trips outside of the home could be flagged and impose penalties.
Perhaps I am just being paranoid after reading a book about radicals in the year 2050. Prior to their secret meetings they all placed their mobiles in a microwave to prevent access from “Big Brother”. The corrupt authorities manipulated tests against insurgents and shipped them off to a penal colony. The book by Phil M Williams is “2050: Psycho Island”.