Apple Watch Ultra 4 review: a more accurate heart sensor, 50-hour battery life, and new AI audio features

Apple Watch Ultra 4 brings three main upgrades: more detailed heart rate measurement, significantly longer battery life, and a suite of AI-powered audio features. The new health sensor system works with the S11 chip to measure heart rate every 5 seconds throughout the day and samples heart rate variability (HRV) 24x more often than the previous model, separating out recovery data from long-term heart health.

Battery life is the biggest leap — up to 50 hours of general use, 84 hours in low power mode, a 15-minute charge adds 18 hours, Extended Workout mode tracks GPS for 25 hours, and Max Extended Workout stretches to 45 hours, enough for a 100-mile ultramarathon. On the audio side, four new features arrive: Sound Recognition, which alerts hearing-impaired users to important sounds like sirens; Live Rewind, which replays a 15-second summary of recent conversation with a double press of the Digital Crown; Siri Recap, which captures key points; and Shazam, which identifies songs automatically — Apple says no raw audio is stored, with processing happening in the S11 chip's Secure Exclave, which deletes audio immediately after use.

The case remains 49mm titanium, available in natural titanium and black titanium, using 45% recycled materials (including 100% recycled titanium). A Readiness Score on a 0–10 scale combines exercise, training load, heart data and sleep quality, alongside a redesigned Health app with a Longevity tab comparing a Health Age score. It runs on watchOS 27 with Apple Intelligence-powered Siri and single-gesture controls. Thai pricing starts at 29,900 baht ($799 in the US), with pre-orders opening September 10 and a US release on September 18; the Thailand release date is not yet confirmed.

Source: Apple