Accurate pulse rate detection is essential for reliable pulse rate variability analysis. On the other hand, minimizing the sampling frequency is essential to reduce the amount of data and computational needs, and consequently the power consumption of mobile/wearable devices, extending their operating hours. Determining the variability of physiological parameters needs a new paradigm since there is a limited possibility of calculating an average eliminating random error of measurement. Finding the optimal sampling rate depends on the actual investigation, the expected variability and variability-changes of the study-population in order to get valid HRV parameters.