InfiniTime: A multi-sensor energy neutral wearable bracelet

Wearable technology is gaining popularity, with people wearing everything "smart" from clothing to glasses and watches. Nowadays wearables are battery-powered and a critical issue is the limited lifetime. So most devices have to be recharged every few days or even hours and thus they miss the expectations for a truly unobtrusive user experience. This paper presents InfiniTIME, a novel sensor-rich smart bracelet powered by small photovoltaic cells, designed to achieve energy neutrality even with modest indoor light levels. Experimental characterization of the fully operational prototype demonstrates a wide range of energy optimization techniques used to achieve the neutrality target. Simulations using energy intake measurements from various deployment scenarios confirm that the InfiniTIME achieves energy neutrality with indoor lighting levels in an office for several realistic application scenarios featuring data acquisition from the on-board camera and multiple sensors, visualization and radio connectivity.