Apparatus for determining a thickness of a wall of a pipe, featuring a signal processing module configured to respond to signaling containing information about traveling stress waves transmitted to and reflected back from a wall of a pipe by a sensor band that includes a series, ring or array having multiple transducers circumferentially arranged and mounted around, and attached to or clamped onto, an outside wall of the pipe; determine a profile of a thickness of the wall of the pipe corresponding to circumferential locations of the multiple transducers based on the signaling received from the sensor band, and the provides corresponding signaling containing information about the profile of the thickness of the wall of the pipe; and another module configured to receive the corresponding signaling and provide a visual indication of either data or a graph of the thickness of the wall of the pipe.