I don't really remember the trainers but even now every time someone produces a really crap version of a hoverboard that is has to be attached to a moving platform that goes along with it or only works on water, or else they do a kickstarter for a real one they always say "like in Back to the Future" - I'm pretty sure the concept wasn't first dreamed up by BTTF but they now the film owns the concept completely and utterly. Just cos they made it look so much fun.