But the app isn't going to work as advertised. Even ignoring people who might maliciously claim to have the virus to cause a local shut-down, with the UK app, someone feeling a bit poorly and being over-cautious could trigger a swathe of people having to self-isolate, and of course anyone who is asymptomatic won't know to press the "warn everyone!" button. But the government will test it in an area with a low incidence of covid-19, claim it's a success and then roll it out over the country and tell people it's now safe to go back to work and mingle with people again. This will result in a new spike of cases and deaths.
I am so weary of being angry at the incompetence of our ruling class. :-(