Design and comfort
Featuring a 1.39-inch circular touch screen, the T-Rex Ultra embraces a rugged aesthetic. The buffed-up dial is crafted from all-metal, with a 316L “marine grade” stainless steel bezel and back panel. The middle frame, made of polymer alloy, extends outward to connect with the straps, while other components such as the buttons and side bridge are also stainless steel.
With that sort of construction, it surely has certifications running on its side. It has passed 15 MIL-STD-810G tests, including those for heat, cold, humidity, ice, shock, and mud. Additionally, it holds EN13319 and ISO6245 diving certifications, ensuring it can operate 30 metres below the water surface.
The watch is likely to withstand extreme physical challenges, but this durability comes at the cost of comfort. The stainless steel and hardened polymer construction make the watch quite heavy. While the thick rubberised strap can handle its weight, users might need some time to adjust.
Moreover, finding the right strap hole for a secure fit is crucial; if the strap is even slightly loose, the weight causes the dial to slip and move. Strapping it too tight can be uncomfortable over time, especially with sweat. However, the strap itself is soft and breathable, thanks to numerous pores and holes along its length.
Display
The smartwatch sports a 1.39-inch AMOLED display in a circular design, boasting a resolution of 454×454 for clear output. Scrolling is smooth, and the display does not feel small despite the watch’s thick metallic bezels. With a peak brightness of 1000 nits, the screen remains bright and clearly visible even under direct sunlight. Overall, the display performs its intended function effectively.
Fitness tracking and GPS
The T-Rex Ultra collects extensive data during workout sessions and features over 100 workout modes. While the watch provides consolidated data, the companion Zepp app offers more detailed insights. The watch has a dedicated workout history option, displaying data from previous sessions, including load during the workout, distance, and average speed for activities like walking and running. It also shows a small map of the route taken, though this map is not very useful on the watch itself.
On the smartphone app, not only is the watch data available, but it also includes detailed charts for improved tracking. Additional data includes maximum and minimum heart rate during the workout, post-workout heart rate, heart rate zones, altitude and gradient distribution, stride length for walking and running, and training effect. The session’s route map is overlaid on the default map service, such as Apple Maps on an iPhone, showing various zones based on activity intensity.
Fitness tracking data on Zepp app
For more accurate GPS tracking, you can select “Accuracy mode” from the workout settings on the watch, which defaults to automation mode for better battery management. To track your position within the Maps app on the watch, you need to download a map section (up to 615 km x 400 km) using the companion app over Wi-Fi, as the watch lacks cellular connectivity.
GPS positioning depends on your location; it quickly positions itself outdoors but takes longer indoors. GPS accuracy also varies with the selected mode. Even in Automation mode, the watch is fairly accurate (up to 50m), while in Accuracy mode, it is highly precise.
 "GPS on Amazfit T-Rex Ultra")
GPS on Amazfit T-Rex Ultra
Health monitoring
The Amazfit T-Rex Ultra offers a variety of health monitoring features, including heart rate monitoring, blood oxygen level tracking, stress monitoring, sleep tracking, breathing counting, and a menstruation cycle tracker for women. Similar to fitness tracking, health indicators provide concise summaries on the watch, while the companion app presents the data more vividly. There is also a one-tap measurement option that tracks all the aforementioned metrics simultaneously and presents a comprehensive health report.
Within the app, the data collected over days and weeks is displayed on graphs, allowing the app to provide trends for each indicator.
 "Health data on Zepp app")
Health data on Zepp app
Companion app
In addition to providing in-depth data for health and fitness monitoring, the companion Zepp app offers various customisation options, including a wide selection of both paid and free watch faces. It essentially allows you to access everything you can do from the watch and more.
The app includes its own App Store, where you can download and install third-party apps onto your T-Rex Ultra smartwatch, although the number of compatible apps is limited. The listed apps are categorised into sections such as utility, productivity, games, lifestyle, and more. Some useful apps are available, such as “Geographic Coordinate,” which uses GPS to determine your location coordinates accurately, even without an offline map of your current location. Besides the app store, you can also manage and change in-app settings for the smartwatch apps directly from the Zepp app on your smartphone.
Additionally, the app provides access to Zepp Coach, a paid-tier service that allows you to choose and customise a training plan based on your fitness goals.
Overall, the companion Zepp app is basic but offers everything you need while using the smartwatch. However, it might take some time to get used to it, as its navigation experience is not the most streamlined.
Battery
Battery life on the Amazfit T-Rex Ultra is commendable, with the company claiming a 20-day battery life, which may even be exceeded based on your usage. During testing over approximately 25 days, I only needed to charge the smartwatch once. While I wore it daily for notifications and call alerts, I also frequently used it for full health monitoring and occasionally for workout tracking with GPS. However, using the “Accuracy Mode” GPS more often will drain the 500mAh battery faster.
For charging, the company provides a dual-pin magnetic charging cable with USB-A type connectivity, which charges the battery from zero to 100 per cent in an hour and 35 minutes.
Who it is for
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Those looking for a rugged smart watches -
Those looking for big battery life -
Those looking to track their fitness data accurately and require GPS accuracy -
Those looking for a companion to track and monitor outdoor activities
Who is it not for
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You want a comfortable daily driver with lightweight design -
You need built-in mic and speakers for calling and voice assistant -
You want support for general apps and features
