Thankfully, I am long past the point where I have to worry about my GPA. But there was absolutely a time in my life when I would have used something like this, had it been available.

I can tell you that my wife's a schoolteacher, and that her school system has a web-based system where parents can log in and check on their kids' grades. She has a lot of parents who check that site religiously. All that is to say that while it may not be a "sexy" site, you've definitely hit on a useful idea here. Good luck!