The cervical spine's range of motion (ROM) is vital for daily activities and musculoskeletal health. Accurate assessment of cervical ROM is essential for diagnosing and managing neck pathologies, such as whiplash-associated disorders and cervical spondylosis. Traditional tools like goniometers and inclinometers, though reliable, face limitations such as inter-examiner variability and accessibility. Objective: This narrative review explores the anatomical and biomechanical foundations of cervical ROM, evaluates traditional and modern measurement techniques, and examines the validity, reliability, and clinical applications of smartphone-based tools for cervical ROM assessment. Methods: A comprehensive review of existing literature was conducted, focusing on studies comparing traditional measurement tools (e.g., goniometers, inclinometers, and 3D motion capture systems) with smartphone-based applications. Key themes included the biomechanics of cervical ROM, the reliability and validity of measurement tools, and the potential of smartphone applications in clinical practice. Results: Smartphone applications demonstrate good to excellent validity and reliability for measuring cervical ROM, particularly for flexion, extension, and lateral flexion. They offer a portable, cost-effective, and user-friendly alternative to traditional tools. However, challenges such as variability in sensor accuracy, user error, and lack of standardized protocols limit their widespread adoption. Conclusion: Smartphone-based applications show significant promise for enhancing cervical ROM assessment in clinical and research settings. However, further research, standardization, and validation across diverse populations are needed to optimize their accuracy and integration into routine practice.