I suppose the difference is what they use the data from the toothbrushes for. OralB produces pretty dashboards with the information while this is a game. I suppose this is closer to your rainbow example.
Another difference would be that this is not a toothbrush in itself so it can be used with multiple manual toothbrushes.
I would agree that holding the smartphone in the other hand is a bad idea. It would be better to prop it up against something or use one of the bathroom kits showed in the video on the page.