Apple App Store: Create app page for upcoming app
Notify is a feature created by Apple which appears to be solely for their Nintendo app launch partnership at this current time. It's not available for general developer program members yet and it is unclear if/when it will be available in iTunes Connect.


  The feature is currently only for Super Mario Run as far as we can tell. Whether it will apply across the entire app store is yet to be determined. It's also unlike the "Pre-order" button from the music and film sections of the iTunes store, since it doesn't give you the option to purchase the content ahead of time.


Source: http://www.cnet.com/news/new-itunes-notifications-will-tell-you-when-mario-is-live/