The diffusion of wireless terminals with multiple com- munication interfaces, e.g., IEEE 802.11, Bluetooth, and UMTS on the same device, is pushing towards the necessity of middleware solutions to dynamically and seamlessly select the proper connectivity technology to exploit at any time. That selection should consider sev- eral elements, at very different abstraction layers, from application bandwidth to energy consumption require- ments, from connectivity costs to user preferences, i.e., it should be context-dependent. The paper presents our context-aware MAC middleware for multi-interface wireless terminals that enables the dynamic determina- tion and selection of the most suitable interface and connectivity provider among the available ones. MAC novelty is primarily in two crucial challenging ele- ments. On the one hand, it considers not only infra- structure-based connectivity providers, e.g., UMTS base stations, but also peer nodes, e.g., neighbor nodes accessible via Bluetooth and connected via Wi-Fi to the Internet infrastructure. On the other hand, MAC can evaluate both infrastructure and peer connectivity providers not only based on usual parameters such as available bandwidth and energy consumption, but also taking into account innovative and crucial indicators such as the degree of mobility, even relatively to mo- bile connecting clients.