A shoe insole has a cavity configured to provide an internal pocket open to a face of said insole, conveniently the lower face, the cavity having a length greater than its width and being directed generally along the length of the insole. A segmented structure is slideably insertable into said cavity within it is removably retained, the segments being disposed along the cavity and housing a pressure sensor, sensor state monitoring circuits, a wireless transceiver and a battery, adjacent segments being electrically connected together and hinged together by pairs of laterally spaced connector bars each mechanically connected together by links configured to maintaining the spacing between segments while permitting flexion between adjacent segments under loads encountered during walking.