Amazfit T-Rex 3 review - The durable smartwatch that's not scared of extreme conditions

The Amazfit T-Rex 3 can be used with both iOS and Android. The smartwatch's operating system is its own Zepp OS 4, which is easy to set up. All you need to do is download the Zepp app from the relevant store, which prompts the user to log in with a suitable account after launch. In addition to a Zepp account (which can also be registered directly), third-party providers are also supported: Facebook, Google, Mi, Line, and WeChat. You cannot continue without one.

Once this has been done, you will be asked to make settings for saving your own location and fitness data, which can be saved generally (default), temporarily in the cloud, or alternatively only on your device. It is also possible to have your fitness data sent to you automatically by email regularly. Numerous authorizations are then requested to ensure a smooth process between the smartphone and the T-Rex.

A device can then be added in the app, the switched-on T-Rex 3 is directly recognized and then only needs to be confirmed on the device; alternatively, the QR code on the display of the smartwatch can also be scanned.

The settings for the watch are a little hidden in the app and can be found under the Profile tab. The charging status of the T-Rex 3 is displayed there concisely, below which there are settings options for health tracking, notifications, watch faces, the app store, and settings for the respective apps on the watch and the shortcut cards. It is also possible to install updates or "locate" the T-Rex 3. Amazfit incorrectly refers to the latter as "locate phone" and causes the smartwatch to vibrate wildly when it is within Bluetooth range.

The T-Rex 3 can also be used to pay with NFC, which is made possible by Zepp Pay. However, the number of supported banks in Germany is low, which is why Amazfit is working with the Irish-British payment provider Curve here.

The watch is primarily controlled via the capacitive touchscreen, but can also be operated in many areas using the four push buttons in the housing. Swiping from top to bottom opens the quick settings. A swipe from the left edge displays the notifications, the app list can be accessed from the right and the shortcut cards are presented from bottom to top. The latter can be both personalized and sorted.

Although the Amazfit T-Rex 3 has a microphone, it does not have a loudspeaker. Instead, it can emit pling and squeaking sounds during training. So there is no need to make calls with the watch, but incoming calls are displayed on it.

App notifications work really well as long as the connected smartphone is nearby. In messengers such as WhatsApp, stickers and photos are even displayed directly on the watch.

The response options are limited to predefined messages (only Android), which can also be customized and sorted in the settings. Don't get confused, the so-called "SMS replies" refer to all messenger apps.

The Zepp app is the central point of contact for all health data on the Amazfit T-Rex 3. The individual topic areas on the start page are displayed in tiles and can be sorted, shown, or hidden as required. The recorded data can be synchronized with Google Fit, Apple Health, Adidas Running, Komoot, Relive, and Strava.

If desired, users can also receive support for their training goals and start a personalized, AI-supported workout with the Zepp trainer. This requires a subscription to Zepp Fitness (20 euros per year). Zepp Aura uses AI for advanced sleep analysis and also offers sleep and meditation music as well as a sleep and wellness coach. The prices here are somewhat confusing: if you book it in the app, you regularly pay 10 euros per month or 70 euros per year, but a gift card in the online store only costs 30 euros for an annual subscription.

The smartwatch tracks all kinds of health data: Heart rate, sleep, blood oxygen, and stress. It can be permanently active or only triggered manually. A digital compass, barometer, and temperature sensor are also on board. The latter is also used for cycle tracking. With the one-tap measurement, pulse, blood oxygen, stress, and the number of breaths are determined within 45 seconds.

At the heart of the Amazfit T-Rex 3's activity tracking is the so-called PAI (Personal Activity Intelligence), which evaluates the recorded data using an algorithm. The value is determined based on age, gender, pulse rate at rest, and pulse rate over the last seven days. The value is higher if the heart rate is increased, for example through intensive training. The watch can also remind you to exercise regularly.

In general, the T-Rex 3 records the steps taken, the distance covered and calories burned, stress, blood oxygen saturation, heart rate, and sleep. On standby, the collected data is used to create a kind of energy monitor. For certain training units (running (outdoor), trail running, track running), the VO2max is also determined and the data is provided in real-time.

The T-Rex 3 records the heart rate and blood oxygen saturation (SpO2), but cannot generate an ECG or measure blood pressure.

In order to better assess the accuracy of the sensors, we compare them with reference devices. For the heart rate, we compare the Amazfit Watch with a Polar H10 chest strap. The measured values are very close to each other. The average values (heart rate), which we determined on a bike ride, are just two beats apart, and the peak rate was rated the same by both devices.

The Braun pulse oximeter 1 serves as a reference for blood oxygen saturation. Here too, both devices are close together and the T-Rex shows a value that is one percentage point higher in comparison.

The Amazfit T-Rex 3's sleep tracking distinguishes between light sleep, deep sleep, and REM sleep. It can also recognize waking phases, which worked quite well in the test and logs both heart rate and breathing rate. From this, the Zepp app then derives the quality of breathing and also determines the risk of hypopnoea (beta). If you add Zepp Aura, you will also receive a more in-depth, AI-supported sleep analysis. The sleep heart rate variability (HRV) is also determined.

The data can be displayed not only for one night but also for weeks, months, and years. However, this comprehensive information is only available on the smartphone; the view on the smartwatch is very limited.

Even the one from the T-Rex 2 is also back on board and adjusts the wake-up times to your sleep rhythm.

The start and stop of the sleep is recognized quite reliably, especially when sleep mode is activated on the smartwatch. This also switches off the display and suppresses annoying notifications.

It is not necessary to have your smartphone with you when training. The Select button (SEL) at the top right takes you quickly to the training area and the last started sport is preselected. The list can be customized to suit your needs. The T-Rex 3 is also the first smartwatch to support Hyrox races.

In the training settings, notifications can be disabled, there is a night vision setting and the pause button can be configured. Training assistants are also available for individual sports; laps, routes, or interval training can be defined. Heart rate zones can also be assigned or adjusted with alarms. Depending on the type of training selected, additional information is displayed, for example, the strokes completed when rowing.

Return route navigation is also available, as is automatic training recognition. The latter must first be activated in the settings and is limited to the sports of squats with your own body weight, front squats with outstretched arms, squats with a barbell, tricep presses, bent-over rowing, bench presses with barbell, sit-up holds and sit-ups with knee touch, Flying exercises with dumbbells, burpees, burpee jumps, overhead tricep stretches, lying tricep stretches, side raises, jumping jacks, lat pulldowns, deadlifts, push-ups, shoulder presses, pull-ups, bicep curls, seated cable rowing, curls with dumbbells, pull-downs with outstretched arms, Russian twists.