Near. Field. Communications.
It seems pretty irresponsible to me that pacemakers and other implantable medical devices are accessible via WiFi and/or cellular data. Communication with the device in question should require a proximity measured in inches. Yes, it might still be possible with a strong transmitter and a sensitive receiver to extend that range to some tens of feet; but in that case the success of the attack is way less likely than one which can be launched from almost anywhere in the world.