The Amazfit GTR 4 includes a microphone and speaker to let you answer calls on your watch when it's inconvenient to pick up your mobile phone. Connect the watch to your mobile phone via Bluetooth to ensure that you no longer miss important calls. The watch's new Bio Tracker 4.0 PPG biometric sensor is enhanced to 2LED, enabling collection of 33% more data than the previous generation, and with improved accuracy. While inspired by the streamlined style and precision of modern sports cars, the Amazfit GTR 4 also keeps one eye on the rear-view mirror, honouring the classics with its vintage round watch body. For a workout motivation boost only your favourite song can deliver, store music on the watch for playback through the built-in speaker or your Bluetooth headphones. The powerful and easy-to-use Zepp OS has been upgraded. Along with super-smooth interactions and a smartwatch-tailored UI that's designed to consume less power, you can now choose from two app menu layouts, and two colour tones, and switch between styles at will.