King Song is a Las Vegas-based company started by several electric unicycle enthusiasts a few years ago. Some of the founders have been working on and riding unicycles since the early 2010s, so they know what separates a good device from a great one. 
In addition, this company has been working together with King Song’s China-based team in hopes of being able to better their devices. You can learn more about the China-based team on their YouTube channel, where they feature most of King Song's products. As for the US-based team, you can learn more about it by following them on their Twitter account.