<p>The growing emphasis on context in mobile devices has become a focal point in mobile and ubiquitous computing research. A typical context recognition system follows a sequential process of sensing, pre-processing, and context recognition, enabling smart sensors to collaborate and deliver diverse contexts for opportunistic sensing applications. This paper presents an overview of smartphone contexts and explores context-awareness in applications such as context-aware authentication and privacy preservation. We detail the hardware sensors employed, their pre-processing, and context extraction, followed by key insights, challenges, and recent research directions in smartphone authentication. Privacy risks associated with outsourcing sensor data underscore the need for robust protection strategies. To address this, we survey privacy preservation techniques from the literature, focusing on contexts most relevant to behavioral context-aware authentication and privacy-preserving applications. Our work uniquely proposes a validated taxonomy and conceptual framework for context-aware behavioral authentication, synthesizes trade-offs across multimodal systems, and introduces a privacy-attack–countermeasure matrix, offering actionable guidance for the design of future privacy-preserving context-aware authentication systems.</p>