Xiaomi is best known as one of the world's biggest smartphone makers, but it is also the world's second-biggest wearables manufacturer thanks to its ultra low price Mi Band fitness trackers. Now, it is looking to build on that success with the Mi Band 2, its third fitness tracker, which, for the first time, features an OLED screen and promises improved heart rate monitoring.

The  original Mi Band, and the slightly upgraded Mi Band 1s, helped Xiaomi pip Apple as the world's second biggest wearable maker in the first quarter of 2016 — based on volume of units shipped — according to figures from research company IDC. The major appeal of these devices is their low price (costing around $15) and Xiaomi is sticking to that winning formula with the Mi Band 2.

The upgraded device will go on sale in China for 149 yuan (around $22) on June 7, though it is unclear if or when the Mi Band 2 will be available in other parts of the world, including the U.S., with a Xiaomi spokesperson telling International Business Times it has no details to share regarding U.S. availability. 

The biggest difference with the Mi Band 2 is the 0.42-inch OLED display, which will show you the time, steps taken and your heart rate. The screen can be activated by tapping it or lifting your wrist as you would a traditional watch to tell the time.  

Heart rate is measured with an improved optical heart rate sensor, which Xiaomi says can now constantly track your heart rate to help improve accuracy. It has also improved the pedometer algorithm, meaning it should be better at tracking your activity.

The band comes with a 70mAh battery, which Xiaomi says is good for 20 days on standby, down from 30 days on the previous models, but it is unclear how that translates into typical use. The device weights just 7 grams and customers will be able to choose between a range of silicone band colors, including black, orange, blue and green.