Nowadays, physical activity (PA) monitoring devices are increasingly popular, with commercially available wearable activity monitors and trackers—hereafter referred to as health wearables—representing a rapidly growing health-focused industry. Health wearables typically cost US$100–250, making these devices relatively cheap compared to research-grade accelerometers (often ≥US$250). In fact, approximately 3.3 million health wearable devices were sold between April 2013 and March 2014 in the United States—representing a sales growth of over 500% as compared to the previous year (Danova, 2014). By 2018, almost 60 million health wearables will be in use worldwide (Sullivan, 2014). The popularity of such devices has risen as they are affordable, stylish, and useful.