There is so many update checker using UIAlertView to notify user to upgrade your app, but the alert will stop user's action. AWVersionAgent will check new version in background and notify user that new version is available from Local Notification.

1. Add [[AWVersionAgent sharedAgent] checkNewVersionForApp:@"your-app-id"]; in application:didFinishLaunchingWithOptions: to check new version in background.
2. Add [[AWVersionAgent sharedAgent] upgradeAppWithNotification:notification]; in application:didReceiveLocalNotification: to response local notification.
3. You can enable debug mode by [[AWVersionAgent sharedAgent] setDebug:YES];.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [self.window makeKeyAndVisible];

    [[AWVersionAgent sharedAgent] checkNewVersion];

    return YES;
}

- (void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification
{
    [[AWVersionAgent sharedAgent] upgradeAppWithNotification:notification];
}

AWVersionAgent is available under the MIT license.