The world of wearables is a wonderful place full of potential but unlike a smartphone or tablet which nowadays has standardized functions, each wearable product can be quite different so buyer beware.
The Fitbit has been the overall category leader defining the overall fitness wearables market. Their products were designed for the everyday person to blend in unnoticed into one's life but still provide a lot of data in a fun to use way. For example, the Fitbit Charge HR is stylish and hip and is there for you when you need it. It is always in the background collecting data so you can focus on more important things in life. But because it is constantly measuring your heart rate, steps, and other activity, the battery doesn't last more than a few days.
TomTom on the other hand, has focused more on the sports enthusiast. While the Multi-Sport GPS Watch acts like a real watch in that it shows time, lasts for many days without a recharge when GPS is not turned on, and doesn't have a power button. It's not as easy to use as the Fitbit but great for those long distance sports like cyclists, runners, and hikers.
The Zepp is also meant for sports enthusiasts but instead of wearing on your wrist, the Zepp is a device that you put on your golf club, tennis racquet, or baseball bat to track your game.
Companies like Fitbit, TomTom, and Zepp need to work with all types of phones, tablets, and PC's. On the other hand, most of the major smartphone companies have also put out their own wearables products but generally make it difficult or even impossible to use them with smartphones from other brands. Samsung and Apple have taken this strategy with their Samsung Gear Fit and Apple Watch, both of which are extensions to their own smartphone brands and can't use be used with other phones.
The Xiaomi Band on the other hand works with other phones and is extremely affordable. For a market leader like Xiaomi to enable interoperability with phones other than its own is commendable and is a great strategy for even more people to become familiar with the Xiaomi brand.
Given the low cost of product development, the diversity in wearables will continue filling every market niche. For the consumer, there will be increasingly something for everyone.