The Xiaomi Watch S4 in Rainbow is a versatile smartwatch designed to balance health tracking with a refined aesthetic. Its 1.43-inch AMOLED display offers a sharp 466 x 466 pixel resolution and a 60Hz refresh rate, ensuring smooth visuals that remain clear even in bright sunlight thanks to a peak brightness of 2200 nits. The build combines an aluminum alloy frame with a stainless steel bezel and scratch-resistant glass, keeping the device durable while weighing only 44.5 g without the strap. Running on Xiaomi HyperOS 2, this watch integrates a wide array of sensors, including heart rate, SpO2, and a barometer, alongside dual-band GPS for precise positioning during outdoor activities. You can track over 150 sports modes and monitor your sleep, stress, and blood oxygen levels throughout the day. The 486 mAh battery supports up to 15 days of normal use, meaning you spend less time at the 2-pin magnetic charging dock and more time on the go. With 5ATM water resistance, the watch is suitable for swimming in shallow water, though it should be kept away from saunas and hot showers. It simplifies your communication through Bluetooth 5.3 calling, utilizing a built-in speaker and dual microphones for clear conversations. This model is compatible with Android 8.0+ and iOS 14.0+, making it a practical companion for users who want a comprehensive health tool that fits seamlessly into a professional or active lifestyle.