FreezCube is a simple device that tells you how much time you have to safely consume frozen food in your freezer in the event the freezer defrosts. The device contains four compartments, each containing a liquid with a different freezing point. By observing which liquid has melted (and thus fallen into the lower half of the device), you can determine how warm the freezer became and how many days the food will keep before it should be discarded. FreezCube is available on Amazon.
photo via The Red Ferret Journal