Like it was said before, this sounds like an interesting concept, but it raises some questions too, mainly pertaining to the payment, the way study time is counted, and the like. For example, if I just leave one of the supported apps open, will that time count? It just sounds a little too easy to exploit for me, I guess. That being said, I think the added stakes might work as good motivation for some people, and the idea of a cash reward for studying even more so. Might give it a try myself.