French 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." The feature is available for all Circular Ring generations starting Wednesday and will become available on the newest Circular Ring 2 once the device ships. Immunity Index resembles a feature called Symptom Radar, which industry top dog Oura Ring revealed last year. It was one of the first features to utilize already-collected health data to warn users of potential strains ahead of full-blown illness. Symptom Radar has caught illnesses a few times since I started using it. Also: This smart ring company will test your blood for $500 - here's what for The rollout of Immunity Index reflects a broader shift by firms in the wearable health technology space to go beyond recording biometric data. Firms are using data collected and artificial intelligence (AI) to predict or even prevent illness. AI advancements and the continued popularity of wearable devices, such as smart rings, will give a long-term boost to predictive health technology.