Abstract: A medical sensor responds to a predetermined condition, such as pressure against a human body area susceptible to ulcer formation, and provides wireless communication of the sensing of the condition. It does this by changing a characteristic of a resonant circuit applied to the sensitive area of the human body and energized by electromagnetic induction. An electromagnetic wave transmitter of a monitoring system is disposed adjacent a support, such as a bed, for the human body. A resonant signal detector is disposed adjacent the support. The monitoring system can also comprise a controller that can compute an exposure time value and/or a shift frequency value. With the foregoing an electromagnetic field is provided across a region of the patient on the support, and resonant signals are propagated in response to the predetermined condition and the electromagnetic field and wirelessly communicated to the resonant signal detector.