1. An apparatus that determines when a monitored individual is likely to exit a supportive structure, comprising: an image capturing device that captures successive images of the monitored individual in the supportive structure; a processing device that processes said captured images to detect predetermined characteristics of the monitored individual with respect to the supportive structure, by comparing a current captured image to a previous image, said predetermined characteristics comprising at least one of a relative position, a velocity, and an acceleration of the monitored individual relative to the supportive structure; and an alarm that is actuated when said processing device determines that said detected predetermined characteristics exceed predetermined threshold values for at least one of said predetermined characteristics.