Inter-Pulse Intervals (IPIs) have been proposed as a source of entropy for key generation and establishment algorithms in Implantable Medical Devices (IMDs) and Body Area Networks (BANs). Most of the proposed protocols built on top of this biometric feature assume that reliable measures of the IPIs are only available to devices maintaining physical contact with the user. However, computer vision techniques have proved to be able to obtain estimates of heart timings from a video recording of the user’s face. In this paper, we study the impact of these techniques on IPI-based authentication protocols, comparing a heart signal captured using a traditional contact-based approach against a signal retrieved using such a contactless technique. One key finding is that quantization is a crucial step in the process and we report our empirical assessment of the main approaches proposed so far. Our results show that up to 70% of the information obtained by means of the contact-based method can be also obtained through contactless techniques.