Our goal is to design and ultimately prototype a communication device that can circulate inside the human body and communicate with a wearable or handheld device such as a cell phone. Despite tremendous efforts in miniaturized medical implants, we are still far from designing micro-devices supporting a communication range of even few centimeters. Main reason is the limitations dictated by the size on powering and communication of such devices. We propose a magnetic-induction communication system that can meet these unique limitations. This paper provides a comprehensive study and comparative analysis of this system.