I have seen some site with very similar concept or strategy but it was about predicting the next price of bitcoin but your is predicting if bitcoin would fall or increases, it's looks attractive and cool but have not check what the odds are I mean like what's the available winings and loss
I've played something like this before but i already forget it what site was that and since there is the same feeling that i get but you know i don't like the idea of predicting things to happen especially in an open market which is a bit hard IMO. But i like the concept since players have their options to choose what would be their best guess. It's more like you were trading yet looks like you were gambling or something.