A smart ring is nothing really new. Oura has a major chunk of the market right now, with Samsung planning to join in with the Galaxy Ring. There are others, but these two are big players in this category. Apple definitely isn’t sitting idle, and are doing research on the viability of this new health-centric wearable. The basic features are definitely powered by sensors for heart rate, pulse, gyroscope, and temperature, but Apple being Apple, there will be features that will differentiate it from Oura and Galaxy Ring. How will Apple Ring work?

First, how will the Apple Ring authenticate? It will, of course, require an iPhone, as a device that small will need storage for its health data. Unlike the others, Apple does not like storing health data in iCloud unencrypted, so it will need to go through the iPhone first. Besides, the Apple Ring will connect via bluetooth or ultra wide band, and not WiFi, for battery efficiency.
Going back to the question, without a screen, a PIN or passcode is definitely out. The Apple Ring will detect when it is worn on the finger, but how do you authenticate it? Maybe you need to confirm connection with the iPhone using Face ID or Touch ID, otherwise, I cannot think of a way to do this.
With the Apple Ring authenticated (dunno how, but let’s assume that Apple figures this out), Apple can leverage its ecosystem and differentiate itself from the rest of the competition. Imagine, Apple Pay, Apple Home Key, extended gestures for Apple Vision Pro, and maybe a microphone for Siri. These along with all the health sensors that are embedded, it is a wearable that won’t cannibalize the Apple Watch market. And oh, no subscription needed, too.
Would I get one? Frankly, I considered getting an Oura ring before, but having a ring on my finger is simply not me. However, if I were to wear it only for sleep monitoring (instead of an Apple Watch), then maybe I’d give this a try.