Override value of RFID tag from external sensor
Yes, there are RFID systems that are designed for this purpose.  They do not "override" the RFID tag per se, but the tag is able to report back the sensor value as part of ts response when queried by the reader.  They are commonly called things like "RFID sensor tags" or sometimes "energy harvesting sensors" for systems where the sensors are powered solely by the RF energy received from the reader.  These are commonly used for environmental sensors, like temperature and humidity, but conceivably any sort of sensor could be used.  Of course if you want a batteryless RFID sensor, the sensor itself must be able to operate on the very limited energy available from the RD reader.  

There are specialized RFID ICs that can be used to create custom devices, several of the major IC vendors have options in this market.