A sensor system and process for measuring electromagnetic activity of a brain are provided. The system and process employ a sensor assembly having a plurality of electrodes arranged in a closely spaced arrangement and a processor to determine a weighted average of the signals indicative of an electric field generated by electromagnetic activity of the brain. The system provides a medical body area network of a subject including one or more of the sensor assemblies and one or more additional sensors, which may be within a smartphone or other wearable device.