GoPro is by far the leading manufacturer and most popular brand for wearable action cams. They hold a monopoly over almost every sporting event, every drone cam, and one of the only action camera markets they haven't penetrated are Russian dash cams.
Xiaomi on the other hand, for those who are unfamiliar with the company, is a Chinese manufacturer that is really dominating Asia. Their phones and tablets are well regarded and sell out within minutes, and the company is not afraid to make new products: so far Xiaomi has released everything from a smart router through to their own line of custom-designed headphones.
The latest rumor floating around the internet involves Xiaomi deciding to enter the action camera market by releasing their own wearable camera to try to capture the emerging Chinese sports market. The rumors suggest that the camera will be manufactured by a Shanghai manufacturer known as Ant Technology, and that it will be released by the end of the year.
How this sort of camera will disrupt the Western market is anyone's guess, but based on Xiaomi's popularity across Asia, it will certainly make waves if it really decides to launch such a product. Xiaomi has achieved a level of trust and popularity for their well regarded smartphones which will naturally roll onto their wearable action camera range, if the rumors prove to be true.
Xiaomi isn't the first smartphone manufacturer to try to compete with GoPro, however, as very recently we saw HTC trying to do the same thing themselves though so far the jury is still out on that effort.