Health Sensing System

At the heart of the Apple Watch experience is the Health Sensing System, which combines redesigned sensors with the S11 chip.

The enhanced hardware allows the Apple Watch to take a passive background heart rate reading every five seconds, all day long. This gives the system a much richer stream of data for evaluating activity, recovery and physiological changes. The additional readings can also improve the accuracy of the Exercise and Move rings by giving the Apple Watch a clearer picture of how the body responds throughout the day.

Heart rate variability, or HRV, receives a similar upgrade, with readings taken as often as every five minutes. Apple separates these into recovery HRV, which can help identify shorter-term signs of stress and recovery, and overall HRV, which offers a broader view of health over time.

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Improved Health app

The improved Health app responds more dynamically to user information.

The Insights tab uses Apple Intelligence to surface timely summaries and deeper observations to make the growing collection of heart, sleep, activity, and fitness metrics easier to understand.

The Longevity tab takes a longer view, examining health information across an extended period rather than concentrating on individual readings. Within it, Health Age compares selected metrics with the user’s actual age to indicate how aspects of their health are tracking over time. It is not intended to replace professional medical advice, but it could offer a more approachable way to understand the relationship between everyday habits and long-term health.

The Health app also introduces guided movement evaluations that assess areas such as strength, flexibility and balance. These use vision-based AI models on iPhone alongside heart rate information collected by the Apple Watch, with an on-screen trainer demonstrating the required movements.

Apple is additionally introducing support for laboratory tests covering more than 50 biomarkers and incorporating results into the Health app. However, this service will initially be limited to approximately 2,000 Quest Diagnostics locations in the US. The redesigned Health app is also launching first in US English, meaning its availability and individual features will vary by country and language.


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Apple Intelligence

With watchOS 27, Apple Intelligence reaches the Apple Watch through Siri AI. Siri AI can draw on broad world knowledge and personal context, allowing users to hold more natural conversations, request wellness information or brainstorm a workout routine without reaching for another device. Conversations can also continue across Apple devices signed into the same iCloud account, including supported images and pinned chats.

The Siri App and Siri Modular watch face make these tools more accessible throughout the day. Elsewhere, watchOS 27 introduces a dynamic app grid containing five Siri-suggested apps, more contextual Smart Stack suggestions and a new single-tap gesture for selecting an individual Smart Stack widget with one hand.


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Audio Intelligence

Audio Intelligence is a new category of features that interpret sounds and conversations using the Apple Watch’s microphone, the S11 chip, Apple Intelligence models in iPhones and Private Cloud Compute.

Sound Recognition listens for important noises such as sirens, alarms, doorbells or a crying baby, then sends an alert to the Apple Watch when one is detected and it can work even when the paired iPhone is not nearby. Shazam can similarly recognise nearby music automatically and show the song and artist in the Smart Stack’s Music Recognition widget.

Live Rewind addresses those moments when a user misses part of a conversation. Double-pressing the Digital Crown displays a transcription of the previous 15 seconds, which can then be saved or used as the basis for a Siri question. Apple Watch plays an audible chime and shows a full-screen animation when the feature is activated, making its use clear to people nearby.

Siri Recap takes a broader approach by generating a title, summary and key points from conversations. Users can decide when it is active, limiting it to locations such as work or disabling it at particular times. It creates concise notes rather than speaker-attributed transcripts, and is designed to exclude sensitive details such as financial information and government-issued identifiers.


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S11 chip

Behind the intelligent Apple Watch capabilities is the S11 chip. It powers higher-frequency health sensing, more precise step calculations, Siri AI and the new Audio Intelligence features, while an always-on processor helps the watch respond continuously without placing unnecessary pressure on battery life.

Crucially, the S11 chip includes Secure Exclave, a hardware-isolated area for processing audio separately from the rest of the system. Audio Intelligence does not create or store audio recordings, and raw audio is inaccessible to Apple, apps, the operating system and even the user. It is deleted immediately after processing, while saved Live Rewind text and Siri Recap summaries are end-to-end encrypted when synced through iCloud.

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