User Referral Plug-In

I was wondering if anyone knew of a plug in that would allow users to get a unique referral link that they could send out to allow people to register. That will then show statistics in the admin panel to show how many referrals each user has made? Something like that

I want to make a competition to give a prize to the user that makes the most referrals. Any plug-in that will allow that will do ?? Thanks everyone!