I consider ANS Analysis the best software program available for measuring all relevant parameters of heart rate variability (HRV). The results are calculated in realtime on the iPad for immediate clinical decision making with graphic documentation of ANS function excellent for billing reimbursement. I purchased most of the commercial HRV biofeedback programs, but ANS Analysis is the most user-friendly and complete package and my #1 choice. Support service is excellent with continual software updates.