so basically, they can hover something over a "special" surface, which is not that impressive
So the "special" surface needs to be anything that conducts electricity but is not magnetic, which is a pretty broad category. https://sg.answers.yahoo.com/question/index?qid=201202290514... has quite a long list.
The images with the lego suggests that they're using copper, which is right at the top of that list for conductivity, but 7 orders of magnitude weaker is plain old sea water, so maybe hendo is not entirely joking about the hovering on water thing ;)