wvmarle:
Attach your sensor wire to the power cable of the fridge. No wires to get caught.Not all fridges are metal boxes. They are often made of HIPS with PU foam as insulator, much cheaper than a metal box, and should let WiFi signals go out just fine.
My fridge has a plastic outer casing, so I'm pretty confident the WiFi signal will get through.
I currently use an off-the-shelf wireless temp sender which uses the 433MHz band to transmit with no problem. The problem with it is that it only has 1 function. Hence the reason I'm playing around with the Arduino stuff to customise something for me.
Cheers