As for the strategy, I would highly recommend you read "Business Model Generation" if you want to flush out this idea a bit more. It seems like you're on the right track, but maybe need to clarify a few points.
Lastly, have you considered going with a monthly subscription based service? Possibly even tiered? I just think that you're more likely to get people to pay $10/mo (with the first 30 days free or something) than $99/year. For recurring subscriptions done easy, check out recurely.com.