Staples offers the Geko Smart Whistle in several colors (Turquoise pictured) for $34.99. Plus, Staples Rewards members qualify for free shipping. (Not a member? Click here to sign up for free.) That's the lowest price we could find by $5. Download the app to your smart device, activate the whistle and it will track you via GPS, as well as alert those on your contact list that you need assistance.