Apple and Google have embarked on their biggest collaboration ever over the past month, building a platform that will turn nearly every smartphone on the planet into a tool for tracking COVID-19. Now, the two companies are providing a first look at how the new technology will work on iPhones and Androids. New screenshots published Monday show how the contact tracing software will use Bluetooth to detect other smartphones in close proximity and alert people if they come into contact with someone who tested positive for COVID-19. Apple and Google will push the new software to people's smartphones automatically later...