While the Oura ring won't alert the user to sleep apnea, one person with an Oura ring looked at the accumulated data from their Oura ring and could see the signs of sleep apnea - https://www.tomsguide.com/features/my-oura-ring-helped-me-di...

Ringconn, similar to Oura without the compulsory subscription, claims to be able to detect sleep apnea with 90.7% accuracy. see https://ringconn.com/blogs/news/understanding-sleep-apnea-an...