Tasks once thought impossible are now within our grasp due to the revolutionary integration of machine learning in personal devices. These devices can diagnose diseases, infer sleep quality, and even augment our cognitive abilities. This chapter examines the interplay of AI, data, and human factors in the context of emerging personal devices. Human factors are complex in nature and multifaceted to begin with, encompassing physical, cognitive, social, and emotional aspects. Neglecting these factors can result in AI systems that undermine human values and do not meet diverse human needs. By considering high-stakes and enterprise/workplace use cases, the chapter uncovers challenges, including data annotation, representation and diversity, and privacy. It situates these challenges within a fast-paced environment wherein powerful AI algorithms are changing the ways humans interact with devices, creating a new paradigm shift. Drawing from the authors’ academic and industrial experience, this chapter reviews the state of the art and sets the roadmap for the next generation of human factors in AI-based devices and applications.