Apple Watch Series 12 and Ultra 4 is expected to ship with a dedicated Readiness app for recovery assessment, storage doubled to 128GB, and a new optical sensor system called Sunstone4p0 designed to improve heart-rate accuracy during dynamic workouts.
MacRumors forum member pdfu discovered these features in watchOS 27 beta code and shared them ahead of Apple’s September 9 announcement.
What the Readiness App Does
The Readiness app is a separate, dedicated watchOS app that assesses how recovered a user is before beginning a workout. It differs from the existing Vitals app, which tracks overnight metrics like heart rate variability and sleep; Readiness answers “are you ready to train today” rather than “what happened while you slept.”
In the watchOS 27 launcher, Readiness appears immediately after the Workout app in the default Home Screen layout, a placement that suggests Apple is placing it as a core fitness feature. This hints at Apple’s intent to compete more directly with premium sports watches from Garmin, which have long offered granular recovery scoring to guide training intensity. By bundling readiness assessment into watchOS, Apple is moving recovery insights from a secondary health monitor to a primary training tool, a distinction that matters to serious athletes and anyone running structured training programs.
Strength Training Captures Individual Sets and Reps
Strength workout tracking will now record individual sets, repetition counts, weight, equipment, body side, and duration. Until now, Apple Watch strength training could only log a crude summary; users who wanted granular per-set data switched to third-party apps like Strong or Fitbod.
The expanded health infrastructure underpinning these metrics makes Apple Watch a legitimate alternative to dedicated gym-tracking apps, particularly for users who prefer keeping everything within the Apple ecosystem.
Sunstone4p0 Improves Heart-Rate Accuracy During Movement
The new optical-sensing system, Sunstone4p0, features lower noise coefficients and wrist- and orientation-based channel selection to improve heart-rate readings when pulse signals are weak and to enable specialized sensing based on how the watch is positioned on the wrist.
This matters most during dynamic workouts: strength training with wrist rotation, pool swimming, or any activity where wrist position shifts frequently. The orientation-aware architecture allows the sensor to switch between detection channels depending on the watch’s angle, solving the intermittent missed or inaccurate heart-rate readings that current-generation watches produce under these conditions.
Internal Storage Doubles to 128GB
Series 12 and Ultra 4 is expected to ship with 128GB of storage, up from 64GB on all previous Apple Watch models. A NAND storage profile tied to the T8320 chip confirms this doubling.
For most users, 64GB was never a practical constraint but for endurance athletes and travelers, it removes a meaningful limitation which allows full Spotify or Apple Music libraries for offline playback during trail workouts, detailed offline maps covering entire regions for ultramarathoners or bikepacking trips, and local data retention for privacy-conscious users who want to sync workouts only when they choose.
Design Remains Unchanged
Series 12 and Ultra 4 will not feature any major design changes compared to the current Series 11 and Ultra 3 models. Apple has maintained the same industrial design since the Series 10 in 2024, opting instead for annual upgrades focused on health features and sensor refinements.
This continuation suggests Apple views the watch’s current form factor as solved and believes users will upgrade for software capabilities, recovery insights, strength metrics, better heart sensing, rather than a new chassis. Whether that bet pays off depends on whether watchOS 27’s health features feel substantial enough to justify an upgrade for existing Series 11 owners.
