According to the complaint filed in U.S. District Court for the Northern District of California, Bal was an early investor in Oura, as well as serving as the company’s “primary marketing arm” in its early years as a cash-strapped start-up.

With an improved design and more features, the Oura Ring 4 has made its way onto my hand for good, but I'm not giving up my fitness tracker just yet

The Whoop band and its app feel more purposefully designed for fitness. While I definitely prefer the Oura Ring as a sleep tracker, the Whoop app and user experience is deeper and more versatile, casting a wide net for all types of athletes and performers.

A potential Oura Ring 5 may be a long way out, but I'm already hoping for these key features and improvements.

Turn your ring stack into a smart one with the Oura Ring, now 15% off for Amazon Prime members. It tracks sleep, stress, activity, and more, and even includes your first month of membership free. Choose from several finishes. The 30-ounce Stanley Quencher is on sale at Amazon for Prime Day. You can get the color "Tigerlily Plum" for just $21.

A travel writer and frequent flier discovered how to avoid jet lag, thanks to her Oura Ring, which is on sale for Amazon Prime Day. Find out how the wellness gadget acts as the ultimate jet lag self-care hack and get one for yourself at Amazon,