Xiaomi, the Chinese smartphone giant, has launched a wearables fitness band that costs only CNY79 ($13). The $13 band is known as the Mi Band. It has sensors for tracking health metrics and it can be used as an alarm clock. The Mi Band can last 30 days on a full charge. It is also waterproof and is on the IP67 standard. The Mi Band can be used to unlock a Xiaomi smartphone.