The B3G (Beyond 3G) networking will enable mobile users to roam freely through heterogeneous networks on an all-IP platform. However, mobility handling in such an environment poses new challenges. Traditionally, mobility protocols such as Mobile IP, SIP and SCTP are used to manage mobility in B3G, but they require telecommunication companies to either modify existing network infrastructures or deploy central entities in the network core to handle mobility. This is not feasible in a fully distributed computing environment (e.g., P2P) and mobile ad hoc networks that are part of B3G networking. As an alternative, this paper introduces a middleware component with modularized functionalities to facilitate mobility management in a fully distributed B3G environment.