Textile electronics represents the ability to improve wearable device systems by providing a distributed system of electronics in that is undetectable to the wearer. These clothing systems uniquely position themselves toward emerging opportunities in vigilant health monitoring. Primary challenges exist in understanding electronics integration that are durable and comfortable to the user, in addition to manufacturing strategies such that the garment is precisely designed for an individual consumer. This presentation explores principles in strategic textile design for improving the efficacy of biopotential sensors and energy harvesting devices embedded within the garment. For biopotential sensors, the dynamics of human movement results in unwanted artifacts in the measurement, but can be significantly reduced when considering the system of textile materials which form the garment. In a similar way, the mechanical and thermal regions surrounding piezoelectric and thermoelectric device integration are critical to obtaining usable levels of power that enable self-powered wearable systems. Finally, strategies for assessing performance of the textile electronics through human use-case scenarios are reviewed.