OK. First, I really don't like apps tha require you to download to the iDevice using a connection to iTunes on the computer. Is it really that big?
Also, I'm not sure I understand how this works. Do I have to add a specific user, and then I receive ALL his or her messages to correct? I wouldn't want to do that. I'd rather have a pool of messages, and be able to correct messages when it was convenient for me, and submit questions when it was convenient for me, too. If the "lemon" points system is in place, it seems like that would work okay.
It seems like a nice idea for a mobile app, though. I am assuming when I say this that it is ad-free, since you will be selling it for a fairly substantial price (in app terms). I would not want to pay $1.99 AND see ads AND have to earn points to use the app function.