You want to find out whether the current iOS device that is running your program has gyroscope hardware available.

Use the isGyroAvailable method of an instance of CMMotionManager to detect the gyroscope hardware. The isGyroActive method is also available if you want to detect whether the gyroscope hardware is currently sending updates to your program (in other words, whether it is active):

- (BOOL)            application:(UIApplication *)application
  didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{

  CMMotionManager *motionManager = [[CMMotionManager alloc] init];

  if ([motionManager isGyroAvailable]){
    NSLog(@"Gryro is available.");
  } else {
    NSLog(@"Gyro is not available.");
  }

  if ([motionManager isGyroActive]){
    NSLog(@"Gryo is active.");
  } else {
    NSLog(@"Gryo is not active.");
  }

  self.window = [[UIWindow alloc] initWithFrame:
                 [[UIScreen mainScreen] bounds]];

  self.window.backgroundColor = [UIColor whiteColor];
  [self.window makeKeyAndVisible];
  return YES;
}