Modular devices consist of a user-interface shell and a detachable communication cartridge. The shell and cartridge both contain unique serial numbers, user-defined passwords, and secret authentication keys, which can be communicated to cartridges and shells, and to a network. A universal wireless device registry system stores serial numbers of integrated devices, device shells, and device cartridges, and other characteristics associated with devices such as secret keys, passwords, screen size, operating system, service usage, and supply chain information. This registry system is able to track communication devices all around the world and is connected to and shares information with computer servers controlled by service providers, manufacturers, and supply chain companies. When shells and cartridges communicate their numbers to the registry system, the registry system can authenticate shells and cartridges. Service providers can also track and control shells and cartridges (as well as devices) based on information from the registry system. Market research can be done using the information associated with each device on the registry system.