System for detecting the evolution of an environmental parameter, comprising: - at least one detection module including an LC resonant circuit sensitive to the evolution of said environmental parameter, configured so as to operate, depending on the value of said environmental parameter, either in a first mode in which said resonant circuit has a resonant frequency contained within a predefined range for which the detection module is able to be detected through magnetic coupling through excitation within said range, or in a second mode in which said resonant circuit has a resonant frequency outside said range or does not have a resonant frequency; - a declaration module separate from the detection module and arranged near said detection module, configured so as to communicate contactlessly in near-field mode even in the event of a variation in the value of said environmental parameter, and configured so as to declare the presence of the detection module; - wherein, in a first configuration, the declaration module includes an LC resonant circuit including an antenna circuit for near-field contactless communication, said LC resonant circuit of the detection module includes an antenna circuit coupled magnetically to the antenna circuit of the resonant circuit of the declaration module, the signature of a frequency response of the antenna circuit of the declaration module being different depending on the first or the second mode of the resonant circuit of the detection module, or - wherein, in a second configuration, the detection module includes a radiofrequency identification chip connected to the LC resonant circuit and an antenna circuit configured so as to communicate contactlessly in near-field mode, wherein said declaration module includes an LC resonant circuit including an antenna circuit for near-field contactless communication and the declaration module includes a radiofrequency identification chip connected to the LC resonant circuit and storing an identifier of the detection module. - at least one detection module including an LC resonant circuit sensitive to the evolution of said environmental parameter, configured so as to operate, depending on the value of said environmental parameter, either in a first mode in which said resonant circuit has a resonant frequency contained within a predefined range for which the detection module is able to be detected through magnetic coupling through excitation within said range, or in a second mode in which said resonant circuit has a resonant frequency outside said range or does not have a resonant frequency; - a declaration module separate from the detection module and arranged near said detection module, configured so as to communicate contactlessly in near-field mode even in the event of a variation in the value of said environmental parameter, and configured so as to declare the presence of the detection module; - wherein, in a first configuration, the declaration module includes an LC resonant circuit including an antenna circuit for near-field contactless communication, said LC resonant circuit of the detection module includes an antenna circuit coupled magnetically to the antenna circuit of the resonant circuit of the declaration module, the signature of a frequency response of the antenna circuit of the declaration module being different depending on the first or the second mode of the resonant circuit of the detection module, or - wherein, in a second configuration, the detection module includes a radiofrequency identification chip connected to the LC resonant circuit and an antenna circuit configured so as to communicate contactlessly in near-field mode, wherein said declaration module includes an LC resonant circuit including an antenna circuit for near-field contactless communication and the declaration module includes a radiofrequency identification chip connected to the LC resonant circuit and storing an identifier of the detection module.