A network mobility device registers with a switch in a telephone network, and receives a first message from a docking station indicating that a mobile device has undocked from the docking station. The docking station includes a Voice over Internet Protocol (VoIP) phone that has a wired connection to a data network, and the mobile device includes a portable digital computing device. The network mobility device receives a call, destined for the mobile device, routed from the switch, and sends an alert message, based on the undocking of the mobile device and the received call, to the mobile device to notify a client of the mobile device of the call. The network mobility device forwards the call, based on the undocking of the mobile device, from the network mobility device to the client at the mobile device via the data network.