The devices were implanted in animals to measure the respiratory and heart beating. (a) A SWG attached to a live rat’s diaphragm to sense the signal from the breath and heart beating. (b) iTENGs were implanted between the heart and the pericardium of swine to sense the ECG and breath. (c) The device was implanted in vivo to record ECG signals of the pig. (d) In vivo energy harvester was provided to measure the motion of the heart.