The new generation of devices and wearables requires state of the art technology to provide seamless solutions for the users. This tutorial-style book on circuits and systems introduces the latest devices and wearables using smart materials for compact and lightweight design. It provides an overview on the fundamental theory of shape memory alloy materials, designing shape memory alloy actuation for different applications, as well as highlighting current devices and wearables using shape memory alloy. Shape memory alloy is a type of smart material that has huge potential to replace conventional actuators due to its high force to weight ratio. The book also includes other examples of medical devices that have been developed. It is targeted for researchers, technical staff, engineers, and students focusing on devices and wearables.