This paper presents the implementation of a combination of hardware and software signal processing methodson a wearable device for the continuous and long-term monitoring and analysis of cardiac activity during insituexperiments. Heart rate assessment and heart rate variability parameters are computed in real-time directlyon the sensor, thus only few parameters are sent via wireless communication for power saving. Hardwaremethod for heart rate measurement, and software methods for the calculation of time-domain and frequencydomainparameters of heart rate variability are described, and preliminary tests for the evaluation of the sensorare presented.1