Diagnostic apparatus for testing heart rate variability, high blood pressure, heart rate, ventricular tachycardia, likelihood of onset of heart attack and cardiac arrest, for medical purposes; heart pacemakers; defibrillators; pulse meters; heart rate monitoring apparatus; cardiac arrest monitors in the nature of heart monitors, heart rate monitors, heart rate variability monitors, blood pressure monitors, ventricular tachycardia monitors, ventricular fibrillation monitors, heart attack monitors; apparatus for use in medical analysis, namely, monitors for determining if the condition of a person's high blood pressure is any of the different forms of ventricular tachycardia, heart attack or cardiac arrest; hematimeters; apparatus for measuring and monitoring blood pressure, heart rate, pulse and skin blood content, for medical use; medical devices for monitoring galvanic skin responses, in the nature of galvanic skin response sensors; optical heart rate sensors for medical use; electrocardiogram sensors, namely, heart rate activity sensors for medical use