We are developing an iPhone application that allow users to send messages to others via Apple Push Notification Service when the target user have installed our application or SMS when haven't.
We want to get notified immediately when our app is uninstalled so that we can decide how to send the message to the target user.
We find the APNS feedback server have a long time delay that doesn't agree with our requirement. So we use another way: when our server recorded the target user have installed our application, we send him message via APNS, if he haven't read the message in 30 minutes, we believe that he has uninstalled the application, so we send the message via SMS.
Is there any way better?
As Oleg said, there is no way to accurately detect if your app was uninstalled.
The APNS feedback service returns a timestamp and a push token for messages it was not able to deliver. Sometimes, this indicates an uninstallation but it can also simply indicate a user that was simply offline at that moment. The Feedback service does have some lag so can not be used for time-sensitive intel gathering.
Based on your requirements, I'd say you're doing it right.
One suggestion that may or may not work for you would be to include a link (via url handler) to your app when you resort to sending an SMS. If it makes sense for the user to return to your app, clicking on that link should launch the app and you'll have a trace on your server if you make a simple call. If, however, after sending the SMS the user is not detected as coming back into the app, chances are highly likely that the app was indeed uninstalled or that the user is offline for an unusually long amount of time which may require some other type of action on your part.
来源：https://stackoverflow.com/questions/10781203/how-to-get-notified-when-our-app-is-uninstalled-in-ios