How to propogate oauth access tokens to other sites then user look to some pic or link with official mac or win client


Looks pretty good idea. Company has twitter account, and twit some offer for their customers. They know customers twitters.
Client open link in official win/mac app to see the offer. Company want to include some personal data for each customer or additional tunnings to offer and common things for potencial clients.

If propogation works and we can get some user id than this is easy task. Than another thing appears - how can we know that this is real user and it is not a bot or something else? If we can get some tokens to be shure?

I understand that oauth design for other things but i think it is interesting scenario.