Wearable computing systems can be broadly defined as mobile electronic devices that can be unobtrusively embedded in a user's outfit as part of the garment or an accessory. Unlike conventional mobile devices, such systems shall be virtually invisible, not hindering physical activity, always active and running without user's attention. We present our wearability driven design approach and the philosophy for a novel wearable computing system integrated into a fully functional belt. This system integrates the main electronics in the buckle of a belt and utilizes the belt itself as extension bus and mechanical support for add ons. The system runs GNU/Linux operating system and has sufficient resources to address a variety of applications in the field of wearable computing. Considerations regarding ergonomic design, system architecture, first implementation results and applications are presented.