This paper presents the first fully passive multifrequency RFID transponder according to the EPC HF and EPC Class 1 Gen 2 UHF standard, containing an on chip temperature sensor and an interface for off-chip sensors. The chip is operating in the frequency range from 13MHz to 2.45GHz, has only two interface pins to a broadband antenna and can power off-chip sensors (e.g. pressure sensors) with a power consumption up to the mW range. The input sensitivity is -10.3dBm and is comparable to despite the additional functionalities.