State-of-the-art passive RFID tags are limited in terms of functionality and operating range due to the limited power that can be converted from the electromagnetic field. This is why state-of-the-art wireless sensor systems are mostly battery-based if a high operating range is required. The proposed ultralow-power on-chip sensor unit and off-chip sensor interface which provides enough energy to supply various sensors with a power consumption up to the milliwatt range make it possible to remotely power the proposed RFID tag and use it as wireless sensor node. Equipping sensor nodes with RFID functionality not only enables identification and logistic applications but also an easy integration of the sensing tag into existing RFID systems. Exploiting the different characteristics of HF and UHF RFID systems, namely the large operating range in UHF and the high available power in HF, increases the flexibility and applicability of wireless sensor nodes. This paper presents a remotely powered multifrequency sensing tag according to the EPC HF and EPC Class 1 Gen 2 UHF standard developed in a 0.13-μm low-cost CMOS process. Input powers of -10.3 or -7.9 dBm at a frequency of 900 MHz are necessary to operate the sensing tag with activated on-chip sensor unit or off-chip sensor interface, respectively.