Amazfit T-Rex 3 smartwatch update brings new map features and improves heart rate accuracy

The Amazfit T-Rex 3 smartwatch is receiving another update, firmware version 3.7.5.1. This release follows the Zepp OS 4.5 update for this wearable, which began in early March 2025, with map improvements, a new Trail Running metric and enhancements for the Readiness algorithm.

Version 3.5.7.1 brings further changes to the map app, such as the addition of mountain peak altitude during a workout and the ability to adjust the map style with a north-up/compass setting. For Outdoor Freediving, Indoor Freediving and Spearfishing activities, users can now view depth changes throughout their workout. Another new feature is support for status indicators on the AOD (Always-On Display) watch face. Plus, CAPTCHA messages can now be displayed in the Notification Center, and you can use a wrist rotation gesture to expand a notification. 

The release notes state that the Resume Later tool has been optimized for enhanced power saving during workouts, and the workout status page design has been refreshed. On top of this, the heart rate measurement algorithm is said to be more accurate when swimming; a Reddit user has confirmed this improvement. Plus, a Facebook user notes that a bug linked to the Cadence Assistant when used for outdoor activity has been resolved, restoring the vibration reminders.

So far, it appears that the version 3.5.7.1 update has only reached US-based users of the Amazfit T-Rex 3 smartwatch (curr. $234.99 at Amazon). It is unclear when this phased rollout will be complete. When it is available in your region, you will be able to download the update through the Zepp App by going to Profile > Amazfit T-Rex 3 > System Update.