An external data processing device to interface with an ambulatory repeater and method thereof is presented. An external data processing device is interfaced in far field telemetric communication with an ambulatory repeater. The external data processing device receives sensitive information preencrypted prior to implant under a cryptographic key uniquely assigned to an implantable medical device over a secure connection from the ambulatory repeater. Physiological measures retrieved from the implantable medical device by the ambulatory repeater are received by the external data processing device over a non-secure connection.