A general interest in “green”, low cost and natural “mimetic” devices now pervades numerous areas of technology and research. These “green” goals have, also, motivated us to explore novel and non traditional approaches for several measurement problems. As an example of such an approach, the study and implementation of innovative sensing technologies based on living organisms (e.g. soil, plants) is presented in this paper with a specific focus on a novel soil-based sensor for measuring static magnetic fields. Following some experimental results, a mathematical model has been formulated and numerical analyses carried out to validate the proposed technical idea. Through our experiments and measurement results, the metrological characterization and validation of the proposed sensor has been accomplished; this shows the suitability of the sensor for magnetic sensing with promising applications in indoor and outdoor security applications.