- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
 NSLog(@"application: didFinishLaunchingWithOptions:");
    // Override point for customization after application launch
 
 UILocalNotification *localNotif = [launchOptions
            objectForKey:UIApplicationLaunchOptionsLocalNotificationKey]; 
 
 if (localNotif) {
 // has notifications
 }
 else {
  [[UIApplication sharedApplication] cancelAllLocalNotifications];
 }
 [window makeKeyAndVisible];
 return YES;
}

- (void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notif {
   NSLog(@"application: didReceiveLocalNotification:");
 
}

- (void)applicationDidEnterBackground:(UIApplication *)application {

    UILocalNotification *localNotif = [[UILocalNotification alloc] init];
    localNotif.fireDate = [NSDate date]; // show now, but you can set other date to schedule
 
    localNotif.alertBody = @"this is a notification!";
    localNotif.alertAction = @"notification"; // action button title
 
    localNotif.soundName = UILocalNotificationDefaultSoundName;
    
    // keep some info for later use
  	NSDictionary *infoDict = [NSDictionary dictionaryWithObjectsAndKeys:@"item-one",@"item", nil];
    localNotif.userInfo = infoDict;
 
    [[UIApplication sharedApplication] scheduleLocalNotification:localNotif];
    [localNotif release];
}

http://iphonesdkdev.blogspot.com/2010/04/local-push-notification-sample-code-os.html

Show a notification immediately after application enter in background (but you can schedule it too)

Schedule app local notification

background, iphone, ios

Objective C