Do you know how Mailbox App did it?

They had a closed beta but they hard a website, a landing page and an iOS Application that enabled people to register in queue waiting for a slot be to accepted into the closed beta.

People had a newsletter delivered to them and were able to share and invite others (this social actions pulled them ahead on the queue). This way people could interact, share and receive newsletters on Mailbox App even though they were not included on the closed beta. It was a successful strategy and other companies did it also with success.

Read this article to know more about it and how you may be able to do it also:
http://techcrunch.com/2013/04/01/queueing-theory-lets-any-app-offer-a-mailbox-like-reservation-system-even-if-its-just-for-building-buzz/