Just wanted to share what I've done. My freezer is in the garage and the outside temp has been ranging from 29 to 45 over night. Well my Johnson Control only works to kick the freezer on and cool, but how was I going to keep my carboys warm.
I've read several posts about lamps, heaters, reptile heaters and whatnot. However, most of those didn't seem appealing, or as safe, and the heating pads you can get for homebrew I didn't think would be as efficient.
I ended up buying a fish tank heater - one that had a temp control built in. After all my tests I thought it was perfect and even more so, I'm 1 week in on my fermenting, with the temp staying at 66 on my carboy, and an outside temp all week of about 30 overnight, I think its a success.
Check it out here http://tpths.co/XqR7yS on my blog Tap This Homebrew - Adventures in Homebrewing