Does anyone have any recommendations?
There seem to be quite a few models around, but no objective information on the range. They mainly seem to have the display on the outside (attached with the equievalent of a fridge magnet) and the sensor inside attached by a cable which goes through the door (and apparently the door seal just shuts right on top)
Google groups didn't throw up a great deal, although there was a posting about an RF model in this ng in about 2004. I found a couple of reasonable pages with some digital models viz http://www.thermometersdirect.co.uk/acatalog/Thermometers_Direct__Fridge___Freezer_Thermometers_7.html http://www.foodsafetydirect.co.uk/acatalog/Fridge_freezer_thermometers.html
I want to avoid the scenario where to find the thermometer you have to open the freezer door and hunt around for the thermometer, thereby letting lots of warm air in and affecting the temperature reading.
The majority of digital models seem to run on batteries, which would be fine, but a mains powered version would be just as good.