The Oura Ring 4 Can Tell You How You Slept or Predict a Cold. Is It Worth It? (opens in new tab)

The Oura Ring, a sleek fitness and sleep tracker that passes as an unassuming piece of jewelry, is seemingly everywhere. It’s on the fingers of New York Knicks, politicians (when Senator Cory Booker of New Jersey wore it during his recent 25-hour floor speech, it logged several workouts), and a prince. You might also see…