Founded in Finland in 2013, the company has been called a pioneer by analysts in the smart ring space. Oura said it has sold more than 2.5 million of its rings since it launched its first product. CCS Insight forecasts Oura will end the year with a 49% market share in smart rings.

Competition is starting to rear its head in the space. The world's largest smartphone maker Samsung made its first venture into smart rings this year with the Galaxy Ring, which some analysts say has put the device category on the map and popularized it with a broader audience.