A wearable sensor device, system and method are provided for monitoring the attention, workload or other physical status of the wearer of the wearable sensor device. At least one biometric index value is formulated for a characteristic status from the processed sensor data of the sensors of the device and the biometric index value may also incorporate prior test data and questionnaire response information in the calculated value. The system may include any number of wearable devices that have sensors, a processor and a communications link as well as a remote computer and a non-wearable device with an interface. The status of the wearer of a wearable sensor device can be monitored with the simple display of the biometric index value as well as the data from the individual sensors.