according to a first embodiment of our invention , a monitoring device is placed above , within , or on the bottom of a cast , boot , shoe , or other lower extremity immobilization or protective device , and has one or more single or cluster of pressure sensitive chambers designed to burst at a predetermined force or weight . the pressure sensitive chambers may be filled with air , liquid , semi - liquid , or particulate material . once properly positioned , the device serves to detect and alert one or more individuals to the fact that weight - bearing has occurred and / or that a certain amount of force has been transmitted across the bottom or other portion of the cast , boot , shoe , mat , sock , insole , or lower extremity immobilization or protective device in a setting where such pressure could be deleterious or harmful .