The effciency of cold supply chain operations can be improved with pervasive 
temperature sensing. In this paper, we investigate the design of a low-cost, 
single-use RFID based temperature threshold sensor that is capable of relating 
the violation of a temperature threshold to a shift in the optimal operating 
frequency at which the tag antenna is well matched to the tag IC. This shift 
is detectable by commercial UHF RFID readers operating in the 902-928 MHz 
frequency band. We will illustrate how state change information is preserved 
using a non-electric memory mechanism that works even in the absence of reader 
transmitted power. We demonstrate that the sensor works reliably for a read 
distance of over 3 m and in noisy environments.