Siren
Notify users when a new version of your app is available
...Siren checks a user's currently installed version of your iOS app against the version that is currently available in the App Store. If a new version is available, a language localized alert can be presented to the user informing them of the newer version, and giving them the option to update the application. Alternatively, Siren can notify your app through alternative means, such as a custom user interface. If an app update is available, Siren checks to make sure that the version of iOS on the user's device is compatible with the one that is required by the app update. For example, if a user has iOS 11 installed on their device, but the app update requires iOS 12, an alert will not be shown. ...