2) I figured you would catch my error in my over simplification. If the balance wheel's rake is perpendicular to the ground, unless the wheel is turned in the direction you're rotating, it will just drag, however, if you introduce a bit of rake (think chopper) then the wheel will pivot on its own in the correct direction. On a car it's called caster and is the reason your steering wheel returns to the center when you make a turn, providing the alignment is correct.
3) This monstrous "appendage" can be replaced with something you probably use every week, a castor. Best known as the wobbling front wheels of a shopping cart. What are they, maybe an inch longer than the diameter of the wheel itself?
4) Before you mention it, if you only used one caster and you leaned into the direction opposite the castor, you'd fall over so you put one on the front and one on the back and hopefully make them of better quality materials than the ones on the shopping carts I always seem to always pick.
5) The ability to turn in its own radius is worth $3000?
6) I'm not knocking the impressive technology but it seems a waste for what is in essence a scooter, albeit one you stand up on.