An intra cardiac device is disclosed. The device comprises means for transforming kinetic energy from heart tissue movement into electrical energy in use, from which electrical energy information in respect of heart function is obtainable. Furthermore, a system is disclosed, comprising one such intra cardiac device and at least one receiver, wherein the intra cardiac device comprises means of communication, through which said at least one device communicates with the receiver(s) wirelessly. In this way energy from heart movement provides self contained intra cardiac devices for conveniently monitoring or stimulating a patient's heart.
