Here you can download the Pokémon GO app for you iPhone, iPad, or iPod Touch (iOS devices). You can even remote install it from you Macbook or iMac!
There are optional in-game purchases available, but the app itself is free to install and play.
The game requires 193MB of free space on an iOS 8.0 or later device.
GPS is not required, but it will improve the playing experience significantly. iPhones are preferred over iPads since the app is formatted for the smaller screen. A data connection is necessary, a 4G connection is recommended if you are not connected to wifi. This information is based on game info as of July 13, 2016.