just about whistles in general,after reading some of the posts here i added one to my dog walking-hiking gear.trying to explain where i was in some Mississippi backwater island,injured,on a cell phone would not be easy..blowing a whistle would help find me after phoning for help..as in--i'm sort of down by the third sandbar island but off in the woods by a creek--someplace..the story of the lady trapped next to a river who could hear voices but not get anyone's attention clinched it for me..