Abstract: Threshold calorimeter/shelf life monitors having a thermally moderating housing containing a liquid solution and one or more low melting point solids all having properties correlated relative to one another and calibrated to closely match a thermal decay profile (time-temperature profile) of a perishable product being monitored and indicate, by a change in color, electrical capacitance and/or impedance, transmitted RF signals, or combination thereof, the cumulative thermal history of the product while in transit or storage and whether its time-temperature profile has been violated to a detrimental extent or if a significant amount of shelf life has been consumed.