This document summarizes several research papers on remote photoplethysmography (rPPG) using RGB camera images to measure heart rate variability (HRV) without contact. It discusses using rPPG to extract pulse signals from videos of human faces to estimate heart rate and HRV. Methods described include selecting regions of interest, reducing motion artifacts, separating pulse signals from noise, and combining signals from multiple regions. The document evaluates these rPPG techniques compared to traditional contact methods and their potential for applications like monitoring drivers' vital signs.