Articles of clothing or pieces of athletic equipment include modules, e.g., for sensing physical and/or physiological characteristics associated with use of the clothing or athletic equipment or for performing other functions. Such systems and methods may use physical or other interaction(s) between the module and the article of clothing or piece of athletic equipment for activating and/or deactivating the module and/or sensing devices included with the module, for confirming whether the module and clothing or piece of athletic equipment 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 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.