Here is another smart ring with various sensors to track your heart rate variability, body temperature, breathing rate, and a whole lot more. The Circular Ring is compatible with iOS and Android devices. It has a vibrating motor to wake you up and alert you to updates. It has changeable outer shells in various colors.
Circular analyzes your bio-signals and alerts you if something unusual is detected. It can also track your sleep stages and helps you figure out how to sleep better. This ring can also track your exercises and show your training zone, activity volume, and recovery time. It lasts up to 4 days on battery.[where to get it]