The application of wearable technologies in monitoring physiological markers of stress and emotion regulation is one of the emerging pathways in digital psycho-oncology that allows for continuous and non-invasive monitoring of some indicators related to the psychophysiological status of cancer patients. Wearable technologies such as smartwatches and biosensors can record data such as heart rate, heart rate variability, physical activity, sleep patterns, and in some systems, indicators related to the skin's electrical conductivity. The importance of this technology in psycho-oncology is that stress and psychological distress cannot always be identified directly and sustainably through individual reporting, and some physiological changes can provide additional information about the patient's condition. Heart rate variability, as one of the indicators studied in psychophysiology, can be considered in the study of autonomic nervous system activity and processes related to emotion regulation, although its interpretation should be done with caution and in conjunction with other clinical indicators. In patients with cancer, pain, fatigue, sleep disturbances, medications, physical activity, and treatment complications can also affect physiological indicators, so changes in a marker alone cannot be considered as an increase or decrease in psychological stress. One of the potential applications of wearables is to provide longitudinal monitoring and identify individual changes relative to each patient's baseline pattern. In this way, instead of relying on a cross-sectional measurement, physiological changes are monitored over days and weeks, and a more accurate psychological assessment is performed if unusual patterns are observed. Combining wearable data with standard questionnaires of distress, anxiety, sleep quality, and quality of life can create a more comprehensive picture of the patient's condition. From an emotion regulation perspective, real-time feedback from technology can help the patient increase awareness of physical status and identify the relationship between stressful situations and bodily reactions. The data can also be used to design personalized digital interventions, such as breathing exercises, relaxation, or short activity breaks. However, the clinical application of this technology comes with limitations. The accuracy of sensors in different situations, differences between devices, body movement, skin posture, and the effect of medications can alter the quality of the data. In addition, the interpretation of physiological data regardless of the patient's psychological and medical background may lead to misperceptions. The privacy and security of health data are also serious challenges, as continuous monitoring of biometric information generates a significant amount of personal data. On the other hand, the continued use of wearable devices may cause some patients to increase focus on physical symptoms or concern about health status. Therefore, the use of wearable technologies should be carried out with informed consent, a clear clinical purpose, and expert supervision. Overall, these technologies can be complementary tools for better understanding patterns of stress, sleep, activity, and emotion regulation in patients with cancer, and develop psychophysiological monitoring capacity in digital psycho-oncology by generating longitudinal data.