Figuratively speaking the Coghlan's Four Function Whistle kills four birds with one stone and is an ideal accessory for the hiker, camper, and trail runner. The Coghlan's Four Function Whistle features a 2 scale thermometer, a pull-out magnifier that folds away when you are done with it, a small compass and of course a whistle. The Coghlan's Four Function Whistle also comes with a spring-loaded clip so you can attach it to your belt, keychain or pack, keeping it close to hand and easy to find.