I found a smart ring that rivals the Oura 4 but costs less (and has no subscriptions)

ZDNET's article highlights the RingConn Gen 2 smart ring as a cost-effective alternative for those seeking affordable wearables with impressive battery life. At $300, it offers a subscription-free option compared to competitors while boasting a 10-12 day battery life, making it ideal for users prioritizing longer usage without recharging. However, the app interface is noted for lacking user-friendliness, and some features like sleep monitoring are underdeveloped with minimal context. Despite these drawbacks, its comprehensive health metrics and affordable price tag make it a compelling choice for those valuing practical functionality over subscription-based services.