There are a number of reasons why it makes sense to use PubNub in addition to, or instead of, push notifications (such as Apple APNS or Google GCM):
- Application is deployed across multiple devices from different vendors, including iOS, Android, Blackberry, etc.
- Developers require ease-of-integration and a consistent interface and behavior across these diverse devices
- Application requires guaranteed delivery of messages which isn't available from the push notification networks
- Push notification networks generally cannot acknowledge message receipt (no bi-directional communication)
- Message payload contains sensitive data which PubNub can deliver securely (SSL) as well as encrypt (AES)
- Message sizes are restricted to 4KB (GCM and MPN S) or 2KB (APNS) whereas PubNub supports up to 32KB
- Messages can be retrieved using PubNub's Storage & Playback
- You can detect who is online with PubNub Presence
- ... and much more.
IMPORTANT: Because delivery is not guaranteed, you should not depend on the remote-notifications facility for delivering critical data to an application via the payload. And never include sensitive data in the payload. You should use it only to notify the user that new data is available.