I built a website that (simplifying here) quizzed users once per day, it wouldn't be too hard to change this into a spaced repetition tool. Would you (or anyon

I built a website that (simplifying here) quizzed users once per day, it wouldn't be too hard to change this into a spaced repetition tool. Would you (or anyone) pay for it? How much? It is interesting enough that I'd be willing to work on it.