How can we create a Magento notification service / API for more than 1 Android device for adding, removing and other operations. If there are two or more devices, it must notify other devices if one of the devices adds, removes or updates a product, user or category, etc. I am using the Magento API. Any help would be appreciated
If you need to build it from scratch, you need to take a look at http://framework.zend.com/manual/1.12/en/zend.mobile.push.introduction.html . Magento already makes extensive use of the Zend Framework, so this would be the easiest solution to implement if you need to build from scratch.
If you are open to a shelf solution, you will need to consider Magento Mobile ( http://www.magentocommerce.com/product/mobile ). This would be the fastest way to get what you want, and most likely would cost less than implementing this API from scratch.
Built on the right is a Push Notification service with a city airship ( http://urbanairship.com/products/push-messaging ).
The solution will cover you right away with Android, and if you need coverage for iOS, you can quickly implement it if necessary.