Implement Push Notification in my iOS App with a Drupal backend
Three module you need to require to accomplish notification one is rules second is services and push notification modules. 

On cofiguration of push notifications you need to configure APNS certificate for IOS by put on private folder and set path to configuration. 

By services module you need call register and deregister push token services. 

By rule module you can set action of send push notification to particular token.