When I was in middle school? maybe high schoo? 1990s somewhere, there was a long article about flywheel batteries for cars, they were claiming some very impressive range and power numbers.

I remember it was one of a million things I read about in sciencey magazines that never went anywhere, but maybe it was the one I was most sad about never happening (at least so far)

The one product I do remember happening that I first read about back then was e-paper! That happened! Cool.