An electronic band assembly comprising: an elongate band configured to be releasably coupled with a wrist-worn watch or a wrist-worn heart rate monitor to form a wrist-worn assembly configured for extending around a wrist of a user and non-invasively engaging skin on the wrist of the user; impedance cardiogram, ICG, electrodes (56, 58, 60, 62) configured for use in measuring cross-body impedance of the user, wherein the ICG electrodes (56, 58, 60, 62) comprising a first pair of electrodes (56, 58) and a second pair of electrodes (60, 62), wherein the first pair of electrodes (56, 58) is mounted to the elongate band for engaging the skin on the wrist of the user, and wherein the second pair of electrodes (60, 62) is externally mounted to the elongate band for contacting by two fingers of a hand of the user on an arm opposite to the wrist of the user on which the wrist-worn assembly is worn; a blood pressure pulse sensor configured to generate a blood pressure pulse signal indicative of arrival of blood pressure pulses at the wrist; a controller coupled to the elongate band, wherein the ICG electrodes (56, 58, 60, 62) are connected to the controller, wherein the controller measures the cross-body impedance of the user via the electrodes (56, 58, 60, 62), wherein the controller processes the cross-body impedance to determine a ventricular ejection time for a ventricular ejection of blood from a heart of the user, wherein the controller is connected to the blood pressure pulse sensor, wherein the controller processes the blood pressure pulse signal to determine an arrival time at the wrist of a blood pressure pulse generated by the ventricular ejection, wherein the controller determines a pulse transit time, PTT, of the blood pressure pulse from the heart to the wrist based on the ventricular ejection time and the arrival time, and wherein the controller determines a relative or absolute blood pressure of the user based on the PTT; a power source coupled to the elongate band and the controller; and a telemetry interface coupled to the elongate band and the controller, wherein the telemetry interface is configured to communicate with the wrist-worn watch or the wrist-worn heart rate monitor via wireless communication. an elongate band configured to be releasably coupled with a wrist-worn watch or a wrist-worn heart rate monitor to form a wrist-worn assembly configured for extending around a wrist of a user and non-invasively engaging skin on the wrist of the user; impedance cardiogram, ICG, electrodes (56, 58, 60, 62) configured for use in measuring cross-body impedance of the user, wherein the ICG electrodes (56, 58, 60, 62) comprising a first pair of electrodes (56, 58) and a second pair of electrodes (60, 62), wherein the first pair of electrodes (56, 58) is mounted to the elongate band for engaging the skin on the wrist of the user, and wherein the second pair of electrodes (60, 62) is externally mounted to the elongate band for contacting by two fingers of a hand of the user on an arm opposite to the wrist of the user on which the wrist-worn assembly is worn; a blood pressure pulse sensor configured to generate a blood pressure pulse signal indicative of arrival of blood pressure pulses at the wrist; a controller coupled to the elongate band, wherein the ICG electrodes (56, 58, 60, 62) are connected to the controller, wherein the controller measures the cross-body impedance of the user via the electrodes (56, 58, 60, 62), wherein the controller processes the cross-body impedance to determine a ventricular ejection time for a ventricular ejection of blood from a heart of the user, wherein the controller is connected to the blood pressure pulse sensor, wherein the controller processes the blood pressure pulse signal to determine an arrival time at the wrist of a blood pressure pulse generated by the ventricular ejection, wherein the controller determines a pulse transit time, PTT, of the blood pressure pulse from the heart to the wrist based on the ventricular ejection time and the arrival time, and wherein the controller determines a relative or absolute blood pressure of the user based on the PTT; a power source coupled to the elongate band and the controller; and a telemetry interface coupled to the elongate band and the controller, wherein the telemetry interface is configured to communicate with the wrist-worn watch or the wrist-worn heart rate monitor via wireless communication.