SelfLoops HRV is a free iPhone application developed by SELFLOOPS SNC DI DEL ROSSO CHRISTIAN E RIBICHINI PIERO. This app is designed to calculate and display heart rate variability (HRV), which is the physiological phenomenon of variation in the time interval between heartbeats. It is used by pro-athletes, Olympians, and university researchers to measure the variation in the beat-to-beat intervals (called R-R).

The app calculates several metrics, including SDNN, RMSSD, pNN50, AVNN, and HRV. The last metric is calculated using the same formula as BioForce HRV and ithlete, which is ln(RMSSD)x20. To use the app, you need a heart rate monitor that adheres to the Bluetooth Low Energy (also called Bluetooth Smart, Bluetooth 4.0) standard. However, it is important to note that SelfLoops does not provide medical advice with this application and recommends consulting a physician or other medical professionals for any health-related questions.