Want to participate in catching monsters in the real world? Sign up now to get in on the early alpha!
Here is the word straight from the official site.
“Eligible players in the United States are currently being invited to participate in a field test for Pokémon GO. The Pokémon GO field test will give users the opportunity to share early feedback and help improve the Pokémon GO experience. If you are interested in participating, visit http://pokemongo.nianticlabs.com/ to register for an invitation. Note that registration does not guarantee access to the field test.”