This brought me back to "clackers." I understand they were known by many names but that's what I knew. A simple device--two colorful plastic balls joined by a string with a plastic ring in the middle to fit on a finger. The idea was to get the balls smacking together. I remember I was in fifth grade and the talented sixth grade girls would charge us a penny for a show of their clacking talent.
I had a pair but never got very good because my mom took them away as some government agency proclaimed them a danger. It must have been a serious message since my mom was never too swift to worry about danger to us kids. She worried enough but didn't freak out like it seems later parents have. I have, of course, been fascinated by them since.
I have no doubt that wheeleys are dangerous. Who knows, maybe more than the crazy stuff I did. But we never wore helmets or other protective gear and we seemed to have survived for the most part. Of course those kids imitating Jackass and insane wrestling are skewing the curve.