I. Introduction
Using smart wearable devices to monitor daily activities has become a major trend for consumers to keep track of their health and fitness. Smart-wear devices such as Fitbit, Apple Watch, and Xiaomi have experienced tremendous growth in recent years. For example, according to the International Data Corporation, the growth in the global wearables market during the second quarter of 2018 was up by 5.5% compared to 2017 with 27.9 million units sold [1]. Furthermore, according to Forbes, worldwide smart wearable device sales will double by 2022, becoming a $27 billion market with an expected 233 million units sold [2].