Twitter Viral loop thingy

I need a twitter feedback loop similar to http://scottdunntravel.co.uk/tram844true so that people can visit my website, tweet about us and receive some free data.

So, in essence, visitor lands on page, sees offer of 50 free marketing contacts if you tweet about us, logs into Twitter, we control text and link, and publishes a tweet. They then go to landing page where we ask what are they would like free contacts in. we then DM them with a URL where they can pick up their data.