The advent of mobile and wearable computing technology has made it increasingly possible for individuals to wear devices that can sense their physiology or health-related behaviors, collecting valuable data in support of diagnosis, treatment, public health, or other applications. In this talk, we describe two research-grade platforms developed in our lab: Amulet and Auracle. The Amulet platform is an open-hardware, open-software wrist-worn computing device designed specifically for mHealth applications; we provide an overview of the platform and of several applications to research. The Auracle is a wearable earpiece that can automatically recognize eating behavior. More specifically, in free-living conditions, Auracle seeks to recognize when and for how long a person is eating. Our experiments show Auracle can achieve accuracy exceeding 92.8% and F1 score exceeding 77.5% for eating detection. Moreover, Auracle successfully detected 20-24 eating episodes (depending on the metrics) out of 26 in free-living conditions.