no need to spend $19 if you don't want to. There are tons of alternatives -
some (well, alot,, OK, most) are made in China, and you may have to wait a few weeks, but I've got a few of these for $3. I use a CR1000 to monitor the temp of a chest freezer fermenter, and since it's C, I also have a $3 back up one of these that can go from C to F with a switch that I use for back up.
Just do a search on digital thermometer remote sensor, or aquarium thermometer (they stick to the outside of the tank, and the probe gets dipped into the water on the end of the 6' cord).