The new Xiaomi Mi Band features an optical heart rate sensor and is designed to track your sleep in a better way than before. The heart rate tracker has been located on the bottom of the device while the strap is made of a better material for enhanced durability. The other features of this activity tracker includes a 45mAh battery capacity sports with a Dialog 4.0 bluetooth chip, ADI sensor and IP67 water resistant. What truly is a unique feature here is the heart rate sensor which comes with high accuracy such as the Apple Watch. The developer testing suggests that the battery life can last for up to 20 days at a time. Available in a number of amazing colors, this is an upgraded and better version of the previous Mi Band for your everyday smart lifestyle.