check the below answer. Its simple idea. You can add 1 minute and then send LocalNotification repeatly.
int myInt=60;
UILocalNotification *localNotification = [[UILocalNotification alloc] init];
[localNotification setFireDate:date];
localNotification.timeZone = [NSTimeZone defaultTimeZone];
[localNotification setAlertAction:@"Launch"];
[localNotification setAlertBody:msg];
[localNotification setHasAction: YES];
localNotification.soundName = soundFile;
localNotification.applicationIconBadgeNumber = 1;
localNotification.repeatCalendar = [NSCalendar currentCalendar];
localNotification.repeatInterval = kCFCalendarUnitSecond;
NSDate *datePlusOneMinute = [date dateByAddingTimeInterval:myInt];
UILocalNotification *localNotification1 = [[UILocalNotification alloc] init];
[localNotification1 setFireDate:datePlusOneMinute];
localNotification1.timeZone = [NSTimeZone defaultTimeZone];
[localNotification1 setAlertAction:@"Launch"];
[localNotification1 setAlertBody:msg];
[localNotification1 setHasAction: YES];
localNotification1.soundName = soundFile;
localNotification1.applicationIconBadgeNumber = 1;
localNotification1.repeatCalendar = [NSCalendar currentCalendar];
localNotification1.repeatInterval = kCFCalendarUnitSecond;
NSDate *datePlusOneMinute1 = [datePlusOneMinute dateByAddingTimeInterval:myInt];
UILocalNotification *localNotification2 = [[UILocalNotification alloc] init];
[localNotification2 setFireDate:datePlusOneMinute1];
localNotification2.timeZone = [NSTimeZone defaultTimeZone];
[localNotification2 setAlertAction:@"Launch"];
[localNotification2 setAlertBody:msg];
[localNotification2 setHasAction: YES];
localNotification2.soundName = soundFile;
localNotification2.applicationIconBadgeNumber = 1;
localNotification2.repeatCalendar = [NSCalendar currentCalendar];
localNotification2.repeatInterval = kCFCalendarUnitSecond;
.....
....
...
[[UIApplication sharedApplication] scheduleLocalNotification:localNotification];
[[UIApplication sharedApplication] scheduleLocalNotification:localNotification1];
[[UIApplication sharedApplication] scheduleLocalNotification:localNotification2];
.....
....
...
How many times you need. you can create repeatly.