Abstract: This application describes a revolutionary device to help prevent the development of pressure ulcers. The device works by using a small number of sensors in the wheelchair or bed to determine and track the projection of the patient's center of gravity (COP) onto the plane of the chair or bed. The sensor data are processed by various algorithms which determine when the danger of pressure ulcer development arises and alerts an attendant to reposition the patient. The repositioning is likewise monitored, and if it is inadequate, a higher-level alarm is issued. This device also maintains a history of patient position and movement, which is potentially useful for diagnostic purposes, such as tracking the degree of improvement resulting from a course of treatment or therapy. The archival record can also provide verification of proper care in the event of lawsuits or insurance claims.