A method and apparatus for monitoring the health and safety of a subject in a room such as a secure room based on video images of the subject. The images are analysed to characterise the movement of the subject as gross movement, fine movement or no movement. In the case of gross movement, no vital signs of the subject are estimated and a display indicates that the subject is moving, but no vital signs are available. In the absence of gross movement, vital signs of the subject such as heart rate or breathing rate are estimated from the video images of the subject, for example by detecting and analysing photoplethysmogram signals in the video images, and the vital signs are displayed. Alerts may be generated if the vital signs are out of the normal physiological range. If vital signs cannot be detected in the video images but the movement of the subject is characterised as fine movement, the display shows that no vital signs are being estimated, but that the subject is moving. If no movement is detected and no vital signs estimate is obtained, then the display generates an alert indicating lack of movement and lack of vital signs.