Articles of footwear and footwear systems include modules, e.g., for sensing physical and/or physiological characteristics associated with use of the footwear or for performing other functions. Such systems and methods may use physical or other interaction(s) between the module and the article of footwear for activating and/or deactivating the module and/or sensing devices included with the module, for confirming whether the module and footwear are authorized for use with one another, and/or for automatic data algorithm selection methods. Additionally, such systems and methods also may use the activation and/or authentication systems for the module for data input to the module. Some examples of such systems and methods may utilize magnets and magnetic sensing systems and/or light (or other radiation) sources and sensing systems for activation, authentication, data input, and/or algorithm selection.