An injectable leadless heart stimulation and/or monitoring system is provided that includes an device having a sealed housing, one or more electrodes configured to electrically contact heart tissue when in use and electric components arranged within the housing. The electric components are at least in part operationally connected to the at least one electrode. The electric components include a power supply for providing power to the electric components. The power supply includes a rechargeable battery and further includes an implant-based coil that is configured to receive electric power via a tuned magnetic or electromagnetic field.
