I would think that if you architect your app to handle disappearing network connections gracefully, it will probably handle the user shutting down the phone gra

I would think that if you architect your app to handle disappearing network connections gracefully, it will probably handle the user shutting down the phone gracefully too. If the battery is critically low, the user will get popups from the operating system at various points and can make a decision whether or not to keep using your application. You could also expose an offline-only option somewhere in your application. A user might want to do this if they are in an area with marginal coverage (e.g., there is a connection, but it's basically useless) or roaming, etc.