Yep! If you have the probe style thermometer, and put it in the middle of the water wiggler, you have more closely approximated the internal egg temperature than if you just stick a thermometer in the incubator. That way, you can tell how much the eggs have actually been affected by temperature fluctuations in the incubator. It is useful to have a thermometer that "remembers" the highs and lows of temperature for this use.