Safety wheels do seem like a good feature that should be standard on these. There's a speed over which they can no longer accelerate fast enough to self-balance

Safety wheels do seem like a good feature that should be standard on these. There's a speed over which they can no longer accelerate fast enough to self-balance, and braking to override the user's questionable decision to go faster would cause a nosedive. What I'm seeing from a quick search is that there's an audible warning upon exceeding the speed that's safe for self-balancing. Ignoring that is rider error.