# Series 12 and Ultra 4 reviews praise the new heart rate sensor, but key features come later

Source: https://idevice.com/series-12-and-ultra-4-reviews-praise-the-new-heart-rate-sensor-but-key-features
Published: 2026-09-17

> The sensor and the Readiness score work on day one. If you are buying for the Audio Intelligence features, you will be waiting until later this year.

The first reviews of the Series 12 and Ultra 4 landed Thursday, and the big change sits under the glass. [9to5Mac's review](https://9to5mac.com/2026/09/17/apple-watch-series-12-and-ultra-4-review/) explains that both watches now read your heart rate every five seconds, moving or not, where older models tried every five minutes while you sat still. That data feeds a new Readiness score, which the review calls Apple's most direct response yet to Whoop and Oura. The Ultra 4 keeps its $799 price and gets up to 48 hours per charge.

Several of the features Apple showed are not ready yet. [Mashable's Stan Schroeder](https://mashable.com/tech/apple-watch-ultra-4-review) wrote that many new features won't be available until later this year, and in Europe there is no timeline at all. "This is going to be a review in progress." The Audio Intelligence features are among the ones coming later, and Readiness needs a week of wear before it shows you a score.

## Sources

- [9to5Mac](https://9to5mac.com/2026/09/17/apple-watch-series-12-and-ultra-4-review/) (9to5Mac)
- [Mashable](https://mashable.com/tech/apple-watch-ultra-4-review) (Mashable)