Best title I could come up with, but to clarify, this is the situation:
I am working on a short url-like service which lets users 'log in' with their Twitter account and post stuff. Now this service could be included in applications such as Tweetdeck and the like.
My question is.. how would I make such a connection? What would be the flow to let another app know some sort of token that can be used with my Twitter-app?
Have you looked into Twitter's OAuth Echo implementation? Quoting:
There are four parties involved in this interaction:
In your case, your service is the Delegator. More info on the documentation.