Abstract: A system and method is provided for extending services to cellular devices. The system includes a wireless gateway having a client side with an intelligent client agent and a server side with an intelligent server agent, a wireless device having a first mode operable in a cellular system and a second mode operable in a wireless local area network and including an intelligent client agent for determining operation mode and for communicating with the intelligent client agent of the wireless gateway and a communications protocol for communication between the wireless gateway intelligent client agent and the wireless device intelligent client agent to effect services. The services include one or more of voice, directory, presence, and media services.

Abstract: A method and system for operating a standalone client in a dual-mode mobile communications device to hand off a call between first and second wireless networks operating under different communications protocols, using Session Initiation Protocol (SIP) and ISDN User Part (ISUP) signalling. The standalone client-side application, or handoff agent, directly controls handoff of the call to the second wireless network until at least one new media stream to connect the dual-mode mobile communications device to the second device is established over the second wireless network. The standalone client-side application solely originates and controls an exchange of messages at the application layer, the exchange of messages modifying the communications channel.