Telecommunication system for automatically locating by network connection and selectively delivering calls to mobile client devices

A mobile communication device comprising:

• software executing from memory on the mobile communication device enabling user selection of one of a plurality of selectable networks for communication, and enabling implementation of transmission and receipt of data in a format compatible with the selected network;
• plural physical interfaces for connecting to individual ones of the selectable networks, the physical interfaces comprise two or more of a wireless interface to a cellular system, a connection interface to a local area network, and a receptacle for a Connection-Oriented Switched Telephony (COST) telephone line;
• and
• wherein the selectable networks include two or more of a Public Switched Telephone Network (PSTN), a cellular telephone network, a Local Area Network (LAN) and an Internet Protocol (IP) packet network and the software enables data communication with the selected network via at least one of the physical interfaces for connecting to the selected networks.