Embedded in mobile devices, private homes, workplaces, and public spaces, sensors have become ubiquitous in modern society. While improving our lives in many ways, the widespread use of sensors also raises serious privacy concerns. Data from everyday sensors often contains intimate personal information and is accessible to various possibly untrusted parties. In addition, advances in data analytics have made it possible to draw detailed inferences even from seemingly innocuous sensor data. This chapter explains why it is important for research to investigate and expose the wealth of personal data that can be extracted from certain types of sensor data. Corresponding publications are needed as a basis for consumer education, risk assessments, privacy safeguards, critical discourse on data protection law, and for understanding the societal impact of sensors. After highlighting the relevance, the scope and limitations of such research are also reflected.