A system for monitoring heart muscle activity of an individual comprising: a first electrode unit for generating a first signal indicative of electrical activity of the heart muscle at a first location on a body of the individual; and a second electrode unit for generating a second signal indicative of electrical activity of the heart muscle at a second location on the body of the individual; wherein each of the first and second electrode units is configurable to operate in a field-sensing mode wherein the electrode unit is configured to generate its corresponding signal based on a detected electric field at a location on or in proximity to the individual's skin; and each of the electrode units comprises a capacitive sensor element, and the capacitive sensor element of each of the electrode units comprises: an electrodynamic sensor which is sensitive to electromagnetic waves; and an antenna comprising an electrically conductive radiating element for receiving electromagnetic waves, the radiating element in electrical contact with a sensing surface of the electrodynamic sensor and having a surface area which is larger than a surface area of the sensing surface of the electrodynamic sensor, the antenna located relatively more proximate than the electrodynamic sensor to the individual's skin during operation of the electrode unit in field-sensing mode; wherein the capacitive sensor element of each of the electrode units comprises an electrically non-conductive layer disposed on the radiating element, characterized in that the non-conductive layer is on an outside face of the electrode unit, and the non-conductive layer is the most proximate layer of the electrode unit to the individual's skin during operation of the electrode unit in the field-sensing mode. a first electrode unit for generating a first signal indicative of electrical activity of the heart muscle at a first location on a body of the individual; and a second electrode unit for generating a second signal indicative of electrical activity of the heart muscle at a second location on the body of the individual; wherein each of the first and second electrode units is configurable to operate in a field-sensing mode wherein the electrode unit is configured to generate its corresponding signal based on a detected electric field at a location on or in proximity to the individual's skin; and each of the electrode units comprises a capacitive sensor element, and the capacitive sensor element of each of the electrode units comprises: an electrodynamic sensor which is sensitive to electromagnetic waves; and an antenna comprising an electrically conductive radiating element for receiving electromagnetic waves, the radiating element in electrical contact with a sensing surface of the electrodynamic sensor and having a surface area which is larger than a surface area of the sensing surface of the electrodynamic sensor, the antenna located relatively more proximate than the electrodynamic sensor to the individual's skin during operation of the electrode unit in field-sensing mode; wherein the capacitive sensor element of each of the electrode units comprises an electrically non-conductive layer disposed on the radiating element, characterized in that the non-conductive layer is on an outside face of the electrode unit, and the non-conductive layer is the most proximate layer of the electrode unit to the individual's skin during operation of the electrode unit in the field-sensing mode. an electrodynamic sensor which is sensitive to electromagnetic waves; and an antenna comprising an electrically conductive radiating element for receiving electromagnetic waves, the radiating element in electrical contact with a sensing surface of the electrodynamic sensor and having a surface area which is larger than a surface area of the sensing surface of the electrodynamic sensor, the antenna located relatively more proximate than the electrodynamic sensor to the individual's skin during operation of the electrode unit in field-sensing mode; wherein the capacitive sensor element of each of the electrode units comprises an electrically non-conductive layer disposed on the radiating element, characterized in that the non-conductive layer is on an outside face of the electrode unit, and the non-conductive layer is the most proximate layer of the electrode unit to the individual's skin during operation of the electrode unit in the field-sensing mode.