On a refrigerated truck, what is the "tape" called that keeps a log of the temperature within?

In an interview for a story I’m writing, a proprietor of a food distribution company was talking about ensuring the food quality of berries on a trip, for instance, cross-country. She told me that on these refrigerated trucks, there is a “ryan tape” (not sure on the spelling of “ryan”) that logs the temperature inside along the entire route. How do you spell this device/what is it?