Detector device arranged to cover at least one portion of a mobile appliance; the device has an electromechanical transducer including a substrate, a first series of electrodes, a second series of electrodes, and a deformable layer associated with the electrodes of the two series, the substrate, the electrodes, and the deformable layer forming a single unit mounted on the portion of the mobile appliance and arranged so that a current flowing between one of the electrodes of the first series and an adjacent electrode of the second series is proportional to a thickness of the deformable layer in register with the electrodes. The substrate including a base layer to which are attached the electrodes of the first series and the electrodes of the second series, which have facing portions, and a variable conduction layer that covers the base layer and the electrodes.