Methods, devices, and systems for monitoring heart rate variability (HRV). The HRV monitoring systems and devices are adapted to give immediate feedback to the subject concerning their current condition and any pertinent changes in their condition. The HRV monitoring systems and devices detect, analyze, and assess HRV against a pre-determined application or user need. They also have the ability to provide real time notifications based on the system's assessment of a user's heart HRV and changes in the HRV.