Trying to create a Trainn style website

My idea is similar to what Trainn does on their freebie websites. I'm using wordpress to create my site. Are there any templates for this sort of thing? I suppose the most important piece of information I need is how website A knows what the user does on website B. IE: how do I know for sure that they've completed an offer, so I can give them earned credit? Any help/templates/point me in the direction of some comprehensive guides/anything would be greatly appreciated. Thank you for your time

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