The Mi Band 2 is a feat of modern engineering; designed to withstand extreme heat, cold, drops and corrosion. It tracks steps, heart rate, speed, sleep patterns and other health data. Information is displayed on an OLED screen in real time so that users can adjust their workout accordingly. If wearers are idle for too long, the device reminds them to increase their activity level with a soft buzz. The bands are available in black, orange, green and blue.