Improvements in the sensor array are disclosed for an array used in a module for preventing unauthorized use of a firearm or other device. The module to which the invention is applicable of the type including a plurality of pressure sensors for sensing a user's handgrip on the device; comparator means for comparing a pressure signature profile compiled from an output from said pressure sensors with at least one pressure signature profile in storage; and means for preventing operation of the device when the compared profiles do not match. The improved sensor array comprises a first set of spaced electrically conductive lines formed on the gripping surface; a thin layer of (preferably) piezoresistive material overlying the first set of conductive lines; and a second set of spaced electrically conductive lines formed over the piezoresistive layer. The lines of the second set are orthogonal to the lines of the first set, to establish a grid-like pattern of conductive lines sandwiching the piezoresistive layer. The projected intersections between the lines of the first and second sets (i.e., the grid crossing points) thereby define with the intervening portion of the piezoresistive layer, an array of sensors which are responsive to pressure applied against the gripping surface by a user of the device. Such pressure changes the electrical conductivity in the path including the intersecting lines and intervening piezoresistive material. Signal outputs from the electrical paths including the array of sensors serve to define the pressure signal profile.