Wireless Fridge Thermometer - Are they accurate?

Accuracy is not as important as repeat-ability. I have found my Acurite wireless thermometer is very consistent with a dial thermometer that I have in the fridge. They almost always are within 2 degrees of each other.
So if you find the wireless reports 2 degrees high or low just take that into account when you take a reading.
I use Energizer Ultimate Lithium batteries(good for -40 f) in my sensors and even in the freezer I get about two years service.