In modern binaural hearing aids, the realization of many advanced functions depends on reliable exchange of information for both sides. Commercially available hearing aids often use RF technologies to meet the communication needs, despite the relatively high power consumption associated with them. In a series of two papers, we describe a low-power communication system utilizing skin conductance designed for binaural hearing aids. Due to the facts that skin contact naturally happens in binaural hearing aids and baseband modulation techniques with low power consumption can be used in transmission over skin, the skin communication system is found to be perfectly suited for the needs of binaural hearing aids. In this paper of the series, system-level design issues are discussed and design specifics of the Medium Access Control (MAC) layer are given, while in the sister paper, low power circuit design and physical-layer algorithms are detailed.