A technique is disclosed for detecting the presence of a certain form of tampering with respect to the operation of a tracking device. The tracking device is of the kind that receives signals from which the location of the tracking device is determined and the tampering that is detected is of the kind wherein signal shielding material is intentionally placed around the tracking device so as to interfere with its ability to receive these signals. In accordance with the present invention, an auxiliary device transmits a signal that mimics certain characteristics of the signal received by the tracking device and from which the location of the tracking device is determined. The auxiliary device is disposed close to the tracking device so that the tracking device is able to receive the mimicking signal from the auxiliary device even when the tracking device is disposed in a location wherein the ability of the tracking device's to receive its location-determining signal is poor or nonexistent. The signal transmitted by the auxiliary device is received at the tracking device and is then processed at such device or at another location to detect whether or not there has been tampering of the type described hereinabove. This processing of the auxiliary device signal may be alone or in combination with other signals received by the tracking device.