Human body communications require energy-efficient transceivers (TRX) to connect diverse devices on the human body for wellness and medical applications. Communication around the human body remains challenging because of the body shadowing effect, energy availability, and form-factor constraints. This presentation highlights the challenges and design considerations to build the Human Intranet (HI) at the physical layer and upper layers. An example of an implementation is presented, using capacitive body-coupled communication (c-BCC) at 450MHz, where surface wave propagation is the dominant propagation mechanism. The TRX implementation is using pulse-based communication, enabling flexible data-rate with ultra-low power consumption. The physical layer and TRX implementations are an important part of architecting the HI, but it is also required to rethink medium access control (MAC) protocols, and especially synchronization of nodes, for efficient communication. This presentation includes details of a novel, flexible, and robust MAC protocol, making use of heartbeat synchronization and addressing the corresponding challenges.