The use of Artificial Intelligence (AI) and the Internet of Things (IoT) for employee monitoring has become increasingly normalised in subordinate employment. Employers deploy these technologies to evaluate work performance, assess personal characteristics, and safeguard property, health, and safety. This legal study, beyond the traditional privacy paradigm, explores the historical and conceptual foundations of the employer's monitoring power, tracing its evolution from the Industrial Revolution to the most recent developments in data science. It highlights how technological innovation has reshaped managerial authority and examines the influential role of technology developers in this process. The study further analyses how these developments affect the enjoyment of employees' fundamental rights within the European Union (EU) legal framework, including the rights to non-discrimination, freedom of expression, and freedom of assembly and association. The book offers a holistic understanding of the employer's monitoring power and examines the conditions for its legitimate exercise under the General Data Protection Regulation (GDPR) and the Artificial Intelligence Act (AI Act).