The performance of a MEMS (Micro Electro-Mechanical Systems) Sensor in a RFID system has been calculated, simulated and analyzed. It documents the viability from the power consumption point of view- of integrating a MEMS sensor in a passive tag maintaining its long range. The wide variety of sensors let us specify as many applications as the imagination is able to create. The sensor tag works without battery, and it is remotely powered through a commercial reader accomplishing the EPC standard Class 1 Gen 2. The key point is the integration in the tag of a very low power consumption pressure MEMS sensor. The power consumption of the sensor is 12.5 mu W. The specifically developed RFID CMOS passive module, with an integrated temperature sensor, is able to communicate up to 2.4 meters. Adding the pressure MEMS sensor - an input capacity, a maximum range of 2 meters can be achieved between the RFID sensor tag and a commercial reader (typical reported range for passive pressure sensors are in the range of a few centimeters). The RFID module has been fabricated with a CMOS process compatible with a bulk micromachining MEMS process. So, the feasibility of a single chip is presented.