Piezoresistive materials are widely studied for the realization of simple and inexpensive strain and pressure sensors thanks to their intrinsic dynamic properties. An idea for designing a passive wireless pressure sensor is proposed. The proposed sensor exploits the variation of surface impedance of a piezoresistive material as a function of the applied pressure. The proposed sensor, differently from classical wired pressure sensors, does not require an electrical contact for reading the pressure level thus allowing its applications in all those scenarios where the presence of wires is inconvenient. The proposed sensor configuration consists of a sandwich structure where a piezoresistive material is embedded in to provide a variable absorption level as different pressure is applied.