In a word - 'Yes!' Whistles have a number of advantages when compared to verbal and hand signal cues. If your dog is out of sight then no matter how reliable your recall hand signal is, it's no good if your dog can't see it! And compared to verbal cues whistles are emotionally neutral - it is far easier to maintain a calm tone with a whistle than when trying to shout a recall cue. And the sound of a whistle travels much better than a shouted word.