[owaislone]

> So far my idea is to encrypt the results of the competition after it is complete. The user would then need to connect to the internet after the competition, log in, pay, and then could get their decrypted competition results. Alternatively, I could just sell it like a normal product, $x/per download...

This would be so annoying for customers. I'm sure your customers will not expect this to happen no matter how many warnings you so and when it does, they'll be furious that you let them use it first and then locked in their data forcing them to pay.

Why not make it a subscription and make the app lock down if it cannot contact your server to verify its subscription key let's say every week or so. Most traditional desktop apps followed this model. It can also let you charge them based on the usage or volume of data so you can have subscription plans. Of course people talented and inclined enough can find ways around it but I wouldn't worry about that as much.