https://www.reuters.com/article/us-health-coronavirus-apps/bluetooth-phone-apps-for-tracking-covid-19-show-modest-early-results-idUSKCN2232A0 >When Singapore launched the first smartphone app of its kind last month to identify and alert people who had interacted with carriers of the novel coronavirus, the city-state of roughly 5.7 million people had 385 cases of infections.