OPPO has revealed that it will release a new version of its fitness tracker soon. This "Vitality Edition" has been hyped as supporting continuous sleep- and blood-oxygen tracking thus far. The OEM should outline its specs in full during its upcoming May 6, 2021 product event, which will also see the launch of the upcoming K9 phone and TV.
https://www.notebookcheck.net/The-new-OPPO-Band-Vitality-Edition-is-teased-ahead-of-its-imminent-launch.535952.0.html