I'm aware of quite a few people who selectively turned their phone off or left them at home in some circumstances, but I'm not aware of anyone who really gave u

I'm aware of quite a few people who selectively turned their phone off or left them at home in some circumstances, but I'm not aware of anyone who really gave up their phone use. In israel, this was done centrally by cell tower triangulation rather than app/os, so no way to opt out even with dumb phones. However, reliability was not very good - e.g. people got notice that they must quarantine because a neighbour 2 floors up was positive, or because they stood outside a wall of a closed room where a positive person was on the other side of said wall. The appeal process was initially non-existent, then slow and cumbersome - so the risk of being "jailed" for 14 days due to false positive was small but serious.