The Verge:

For those who haven’t been following the title’s development, the game uses your smartphone’s camera and sensors, as well as location-based algorithms, to place pokémon in the real world. That way, as you travel around to landmarks and notable locations in your city, you can catch the creatures and then train and battle them at gyms.

Looks like the game is currently available in New Zealand and Australia, not yet rolled out in Japan and the US. Sounds like it’s just a matter of hours or days, though.