Abstract: What is provided is a system, method, and article of manufacture for detecting, monitoring, and tracking whether a user is in a more relaxed or stressed state by measuring the user's heart rate variability. The system has a heart rate monitoring device with at least one sensor that is configured to measure user heart rate. The system also has a mobile computing device, which may be configured to interact with the heart rate monitoring device for monitoring, tracking, and displaying a user's heart rate and mental stress level information. The method measures the user's heart rate information to calculate a measure of heart rate variability and to analyze whether peaks corresponding to activation levels of the user's parasympathetic nervous system (PNS) and sympathetic nervous system (SNS) exceed a predetermined threshold level within a predetermined time period.