Objective-C:
UIBarButtonItem* cameraBarButtonItem =
[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCamera
target:self action:@selector(myCameraAction)];
Swift:
let cameraBarButtonItem = UIBarButtonItem(barButtonSystemItem: .Camera, target: self, action: "myCameraAction")
Это создаст UIBarButtonItem со значком системного элемента камеры.