Nike Inc. (NYSE: NKE) has filed a lawsuit against Lululemon Athletica Inc. (NASDAQ: LULU), accusing the apparel company of patent infringement over its at-home Mirror fitness device and accompanying mobile apps. What Happened: Nike said in its lawsuit that it owns a robust portfolio of patents directed to its digital sport innovations for use in or with fitness equipment and apps, citing the Nike+ iPod system, the Nike+ SportWatch, and the Nike+ Running App, among others.