Android and iOS push notification implementation

We need sample apps to help us implement push notification in our existing android and iOS apps. We already send notification to the apps but when the app is in the background the user may miss the notification. We need the notification to either bring the app to the foreground or sound an alarm for one minute. We are open to adding new functionality such as audio or voip communication to the apps if that is required.

You can quote for both or either of the iOS and Android apps.