Three smart watches in Chinese firm Zepp Health’s Amazfit range test four health metrics – heart rate, blood-oxygen, stress level and breathing rate – in one tap in as little as 45 seconds.

The GTR 3 Pro, GTR 3 and GTS 3 use Zepp OS, an operating system tailored to optimise the performance of Amazfit smart wearable devices instead of transferring a power-draining smartphone OS to users’ wrists.

Built around the concept of being light, smooth and practical, this OS should enable easier interaction and help users eliminate tedious operations with lower power consumption.

It also works across Android and iOS devices, and connects to popular health platforms, such as Apple Health or Google Fit, to sync health data, and Strava, Relive, Runkeeper and TrainingPeaks to sync and share sports data.

There are up to 150 watch faces with matching always-on displays, as well as dynamic effects and smooth animations. Wearers will even be able to design their own watch faces and mini apps with the app developer kit that is coming soon.

The watch can test four health metrics in one tap thanks to the built-in 6PD (photodiodes) BioTracker PPG 3.0, which measures heart rate, blood-oxygen, stress level and breathing rate in as little as 45 seconds.

The technology monitors the wearer’s heart rate all day, even while swimming. Alerts for abnormally high or low heart rates, as well as tracking heart rate zones, let wearers optimise workouts.

Current health and wellbeing are calculated instantly and converted into a single PAI (physiological activity indicator) score, collated from data based on the past seven days of activity.

Wearers can monitor light, deep and REM sleep stages, plus waking times during the night, daytime naps over 20 minutes, and even sleep breathing quality. Users can check sleep data directly on the watch.

It also includes menstrual cycle tracking. After recording the menstrual period, users can intelligently and intimately predict the time and length of the following menstrual and fertile window.

With Alexa, users can set an alarm, ask a question or more when online, and when offline, use the offline voice assistant to open a sports mode or health feature, or even access Home Connect to control smart home devices.

GPS location tracking is based on five satellite systems.

Motivation tools let wearers track their runs with the optional Virtual Pacer, then optimise progress and recovery with the PeakBeats performance algorithm.

The Zepp OS also comes with health and fitness insights, and the Zepp app on a smartphone serves as a hub where users can access additional advice to help them achieve their goals.

As the premium choice in the series, the GTR 3 Pro smartwatch has a 3.7cm, 331ppi AMOLED ultra HD display. It has a 70.6% screen-to-body ratio. Whether firing up activity tracking through one of the 150 built-in sports modes, or monitoring stress levels, this watch lets users stay aware of health round the clock. A 450mAh cel provides up to 12 days of non-stop battery life on a single charge.

Made from lightweight yet durable aircraft-grade aluminium alloy with an elegant rotatable crown, the GTR 3’s bezel-less design seamlessly integrates with the curved glass screen to give a heightened sense of immersion. Sporting a 3.5cm AMOLED HD display, the watch is powered by a 450mAh battery for a battery life of up to 21 days.

With a square 4.4cm, ultra HD AMOLED screen with 341ppi, the GTS 3 is one of the slimmest and lightest smartwatches around, yet still has a 72.4% screen-to-body ratio.

“These three watches achieve the promise of smart health made easy,” said Wayne Huang, CEO of Zepp Health. “The GTR 3 Pro is built to empower. The Amazfit GTR 3 is built to last. And the GTS 3 is built to move. We hope you are as excited for this new generation as we are. Connecting health with technology is the core philosophy behind the Zepp OS. And so we created the Zepp OS to be a health-focused operating system that helps our watches achieve our mission of making it easy for everyone to live a healthy life.”

Amazfit products are available in more than 90 countries and regions worldwide, across North and South America, Asia, Europe and more.