I performed a test that might interest you.
My temperature sensor / clock (shown in the link above and in the accompanying photos) is 433Mhz. I installed the sensor in the TT fridge and checked wireless strength. At over 35' distance from the fridge - as well as through the fridge walls, campers walls, one exterior house wall and one interior house wall...I could still get signal from the wireless temperature transmitter in the fridge. (the fridge was not turned on)