The invention is directed to a system for acquiring electrical footprint of the heart, electrocardiogram (EKG or ECG) and heart rate variability monitoring, incorporated into a mobile device accessory. The ECG signal is conveniently acquired and transmitted to a server via the mobile device, offering accurate heart rate variability biofeedback measurement which is portable and comfortable during normal daily life. The invention provides a reliable tool for applications such as wellness, meditation, relaxation, sports and fitness training, and stress-relief therapy where accurate heart rate variability measurement is desired.