Accurate and inexpensive psychophysiological equipment and software are needed to measure and monitor the autonomic nervous system for gaming and therapeutic purposes. The purpose of this study was to determine whether heart rate variability (HRV) derived from photoplethesmography (PPG) technology was predictive of autonomic nervous system (ANS) aging or biological age. Second, we sought to determine which HRV variable was most predictive of ANS change and aging. To test our hypotheses, we first conducted a criterion related validity study by comparing parameters of a 5 minute resting HRV test obtained from electrocardiography (ECG), the current "gold standard," with PPG technologies, and found them to be significantly correlated (r>/=0.92) on all parameters during a resting state. PPG was strongly correlated to ECG on all HRV parameters during a paced six breaths per minute deep breathing test (r>/=0.98). Further analysis revealed that maximum variation of heart rate had the highest negative correlation (r=-0.67) with age. We conclude that PPG is comparable to ECG in accuracy, and maximum variation of heart rate derived from a paced breathing test can be considered a marker of biological aging. Therapeutic interventions and games designed to reduce dysfunction in the ANS can now be developed using accurate physiological data.