Abstract: A device for the prevention or treatment of ulcers includes an absorbent layer 20 and an upper layer 30, 84 which may be transparent or opaque, and is preferably curved downward to engage the absorbent layer and minimize contact to the ulcer. A sensor or signaling member is provided for outputting an electrical signal in response to the flexible deformation of the upper layer indicative of the excessive pressure. A warning member, such as a light or alarm, is responsive to the signaling member for notifying the patient or caregiver of excessive pressure. In another embodiment, the device includes a plurality of shear detector sensors for outputting an electrical signal in response to shear movement between the absorbent layer and the patient's skin.