This one <a href="https://www.youtube.com/watch?v=xbTQoFjOAdM" rel="nofollow">https://www.youtube.com/watch?v=xbTQoFjOAdM</a> looks like something simple enough that you could maybe sell it to families? Like, instead of installing a playground, install this coaster.<p>I'm not sure what the safety/liability situation would be like, but the coaster is close to the ground—if the child wears a helmet I don't <i>think</i> this would be more dangerous than a set of swing set or jungle gym?