I got one of those wireless themometers and put the sensor in the coop. It is great the know the temp - gives me peace of mind. I got mine from Lowes for ~ $13.
Here is my water heater;
I created a box at the height and size to hold a "plant light" then removed the hanging part. It stands on its end which is sturdy. I then covered the top with metal flashing and cut out a small piece of non-skid material to stand it on. The light bulb I have in it is a...