I want a tool that will monitor for a specific tweet, and when it occurs associate that tweet with a user on my site and perform an action on that user.
Specifically, I want to offer a free trial extension to users that tweet they are using my site.
I don't want to make the person do an OAuth thing and log into a tool with twitter. I'd prefer the user clicks a link and goes directly to a pre-authored tweet. Then they click the tweet button, and the system later recognizes it from the twitter stream.
So I imagine it should somehow tag the tweet message going out (maybe with a unique bit.ly address or something) to tell how the twitter user maps to my app's users.
Any tools that do this already?