CEOs and celebrities love Oura’s sleep-tracking ring. Its CEO has a plan to stay ahead of Apple and Google

One of the Apple Watch’s biggest threats has no screen, weighs about a fifth of an ounce and charges a monthly subscription for most of its features. Yet the Oura ring is on pace for $1 billion in sales this year, boosted by its presence on the fingers of celebrities including Jennifer Aniston, Gwyneth Paltrow and Michael Dell.