Wireless Fridge Thermometer - Are they accurate?

The wireless ones (Well the quality ones) are more likely to be accurate but you need to know how to calibrate them This can best be done at 32 degrees but depending on how accrate you want them you will need DISTILLED water and of course a water proof "Sleeve" for the transmitter.

one indication of accuracy is to put the two units (indoor and remote) side by side.