Zeblaze Crystal MTK2502 Bluetooth 4.0 and 1.54 Inch Leather Strap Waterproof Smart Watch (Silver) MTK2502 chip with Bluetooth 4.0: Adopting the latest MTK2502 chip, has more perfect compatibility with iOS and Android system than most normal chip. HRM heart rate monitor: Zeblaze Crystal'sHRM heart rate monitorfunction will give you the real-time feedbackas Apple watch. Let you know about your heart rate anytime and anywhere. Call / Message reminder: When a call or message coming, Zeblaze Crystal will remind you. Pedometer / Sleep monitor / Sedentary reminder: Taking caf? of your life, help you develop good living habits.