Circular/ZDNETFrench smart ring brand Circular has launched its Immunity Index feature that could notify you ahead of your next cold. The feature, available on the smart ring’s app, uses health data the ring already aggregates, such as heart rate variability, resting heart rate, sleep-breathing regularity, and temperature stability, to predict strain on the body ahead of illness. Also: This subscription-free smart ring gave my Oura a run for its money (and it’s cheaper too)Immunity Index monitors these biomarkers to detect changes and raise a red flag if something’s awry. It rates your immunity out of eight, with eight out of eight meaning you’re in the clear, six out of eight meaning there are slight issues, four out of eight meaning you’re slightly vulnerable to sickness, two out of eight meaning advanced risk, and zero out of eight meaning you’re at major risk of illness. Users can couple the Immunity Index with the “Log Symptoms” feature to track their daily symptoms and feelings. Also: Finally, a smart ring I don’t have to charge every night (and no subscription)”With the Immunity Index, we’re shifting the health conversation from reactive to proactive,” Amaury Kosman, CEO and co-founder of Circular, said in a press release. “Our goal is to empower people with real-time insights so they can take small, smart actions before minor fatigue turns into full-blown sickness.” More