
Most health and fitness monitors are worn on the wrist. The OURA Ring is different: it is (as its name implies) worn on a finger. The company claims the ring tracks sleep and activity with “unparalleled precision.” It senses arteries in the finger, taking 250 samples per second.
The unit can be worn while swimming. It automatically turns off Bluetooth while the user is sleeping. However, the battery can only operate two to three days before it needs recharging.
For sleep monitoring, the firm claims the OURA Ring measures total sleep time, deep sleep time, REM sleep, sleep efficiency, sleep latency (how long it takes you to fall asleep), restless sleep, and sleep timing (midpoint of sleep). However, the website descriptions are ambiguous. For instance, deep sleep is defined as “when your blood pressure drops and your heart and breathing rates become regular.” Does the OURA Ring measure heart rate, respiration rate, and blood pressure? Like an oximeter, it should be able to measure heart rate. And the firm states explicitly that it measures skin temperature. The “full technical specifications” say nothing about what sensors are used, what they measure, and how accurate they are.
The website's front page says the OURA Ring “Detects blood volume pulse, body temperature and activity level with advanced sensors.” My guess is that everything is based on these three measures. There is no way to know how useful the company’s proprietary “readiness score” (insights about your well being) is without trying it out.
The OURA Ring is pricey at $299 for artic white and mirror black models, and $499 for stealth black. The unit comes with a charger. The associated iOS and Android apps are compatible with phones from Apple, Huawei. LG, Motorola, Nexus, Samsung, and Sony.