The Apple Inc. Apple Watch 5 is displayed after an event. (Photographer: David Paul Morris/Bloomberg)
(Bloomberg Businessweek) -- Petri Hollmen was feeling fine the morning of March 12 when he got a troubling reading from the smart ring he wears to track sleep. His “readiness,” a well-being indicator measured by the device, was registering far below normal. The Finnish entrepreneur wasn’t feeling any of the symptoms associated with the novel coronavirus, but because he’d recently returned to his home in Turku, Finland, from a ski tri...