The present study was performed to compare R-R interval data and heart rate variability indices obtained from the Polar S810i and the Omega Wave Sport System for a total of 96 adults in a supine position. Data were simultaneously recorded with the Polar S810i and the Omega Wave Sport System and processed by unique software. Bland-Altman analysis for the R-R intervals shows minimal bias for free and paced breathing. No significant differences were observed for heart rate variability indices derived from the signal from both devices, except for the power of the high frequency band and the acceleration changes index during either free or paced breathing. Coefficients of correlations were all above 0.96. These data suggest that both systems are valid to record R-R interval signals and to obtain a valid analysis of heart rate variability. However, Omega Wave Sport System enables data to be collected without any artifacts making the analysis of heart rate variability easier than the analysis of Polar S810i. Nevertheless, Polar S810i continues to be more practical in clinical and applied situations due to the affordability of the device.