I have heard of thermostats that plug into an outlet with a probe that goes inside a fridge, and you use it to keep beer fermenting at an "ideal" temp. You may be able to use something like that, but I have no idea what they are called or where to look... I guess google? ebay? amazon?
EDIT: Google search for Beer Fermenting Thermostat, 1st result
http://www.northernbrewer.com/temp-control.html
Looks like you plug in to the wall, and plug your fridge into it, use it to set the temp for the probe to kick on at. Not sure if it works for heating or just cooling, but you can look for more online also.