Nowadays, wireless networks with heterogeneous technologies are largely deployed and, mobile terminals have multiple interfaces to access these networks. This raises many research issues such as the simultaneous access to heterogeneous networks and the mobility management. This paper proposes to manage the mobility of a terminal in this context. In particular, we want to guarantee that, while a terminal is moving from a given network to a different one, the quality of service of its applications will be maintained. For this purpose, we combine a multi-homing protocol (SHIM6) with an IMS architecture. The protocol SHIM6 ensures a seamless change of networks without any application disruption. The IMS architecture allows the establishment of multimedia session with quality of service. Our solution can manage the inter-domain mobility of a terminal in a reactive and proactive mode. For this purpose, we implement a SIP proxy inside the mobile terminal. The experimental evaluation shows the feasibility of the SHIM6-IMS integration and a considerable reduction of the handover delay.