A computer user interface device is provided, made up of modules having separate sets of user interface features. For instance, a keyboard device has a first module bearing standard alphanumeric and control keys, and a second module, selected from a set of optional modules bearing specialized features such as multimedia controls, communication interfaces, or magnetic media readers. The modules are mechanically coupled together. An electrical interface allows user input signals, such as keystroke signals, to be consolidated on one module, preferably the specialized module, into a single signal stream, for coupling to the computer.