I can't imagine what a treadmill design that is safe for children the age of the those in the video -- my guess 3 for the boy and 5 for the girl? -- to play on would be. If for no other reason than they can turn it on to a speed which will chuck them off. Or stick their fingers in the belt, etc.
If you're saying kids shouldn't play on them unsupervised, I agree. But for those ages, the same thing is true of a bicycle. I'm just objecting to the notion that there's no difference between a bicycle or a treadmill and a circular saw as far as using them around children goes.
