Method and apparatus for determining the state of entrainment between biological systems which exhibit oscillatory behavior such as heart rhythms, respiration, blood pressure waves and low frequency brain waves based on a determination of heart rate variability (HRV). Entrainment reflects a harmonious...http://www.google.com/patents/US6358201?utm_source=gb-gplus-sharePatent US6358201 - Method and apparatus for facilitating physiological coherence and autonomic balance
