They propose some haptic warning, so presumably those devices lacked any warning at all. I have owned some of similar monocycles and they all at least emitted a

They propose some haptic warning, so presumably those devices lacked any warning at all. I have owned some of similar monocycles and they all at least emitted a sound and had options in settings to prevent you from using full power of the motor for horizontal motion (it basically kicks you back gently once you reach the treshold and that makes you feel like you're about to fall and you lean to the opposite side way before one reaches close to 100% power).