This book is a short introduction to the principles and techniques behind designing effective voice user interfaces. Drawing on years of experience designing and implementing user-centric telephony voice systems, the authors present a short and highly accessible tract on how to design effective voice experiences for portable electronic devices in the form of wearable technology. A whole new class of use cases -- mainly those where either the eyes or the hands or both are busy -- can now be easily enabled by an effectively designed wearable pure voice interface. Actions that would normally take 10 steps or more on your iPhone (even with Siri) can be effectively carried out in 2 or 3 steps: you want to check the weather? Forget your iPhone. Instead, talk to a little device that's on your shirt collar and say, "Weather," and the weather conditions and forecast are read to you. Wearable Voice is the Next Big Thing in the world of User Interface (UI) design and this book presents one of the first systematic practical guides to effectively delivering such UIs.