Device having electromechanical transducers for detecting approach and/or contact in a motor vehicle

A device for a system for detecting contact with and/or an approach toward a motor vehicle, the device being configured to be mounted on said vehicle, the device comprising:

• a) a vibration generator, which comprises:
• a first electromechanical transducer, configured to generate a mechanical movement in response to an electrical excitation signal, and configured to be mounted on an external element of said motor vehicle;
• and
• an electrical signal generator, configured to deliver the electrical excitation signal to the first electromechanical transducer, the electrical excitation signal oscillating at an excitation frequency;
• b) a rechargeable energy storage device, configured to supply electrical energy to the electrical signal generator;
• and
• c) a vibration sensor, consisting of a second electromechanical transducer that is configured to generate an electrical response signal in response to a mechanical displacement and to be mounted on said external element of the motor vehicle;
• wherein an output of the vibration sensor is electrically connected to the rechargeable energy storage device such that, during use, at least part of the electrical response signal recharges the rechargeable energy storage device.