I have been using a remote thermometer in my coop for two years now.
In fact, I can tell you as I sit here typing in my computer/living room, that it is 55 degrees in the main henhouse. Temps over the past 24 hours have ranged between 59 degrees and 39 degrees in the henhouse.
I love the thing! During the summer, it warned me when the hens were having to endure conditions too hot -- when I saw it hit 100 degrees several days in a row, I went out and bought another fan for them. Last year during the ice storm, I was able to monitor the cold as well.
Remote temp readings remind me and my wife to bring the chickens warm treats during the winter, and cool treats during the summer. We time the arrival of their warm milk or oatmeal treat with the temp inside the henhouse during the winter, and we make sure that when the temp reading goes high during the summer that we get in there with ice water or cool watermelon or whatever cool treats we have.
I installed the remote thermometer when we originally built the coop, and have never been without it.
One problem that you could have is that the thing can run out of battery power at the most inopportune times. The remote sensor is a transmitter, and it takes power to send transmissions back to the receiver inside the home.
Some models are more frugal with the battery power than are others, but eventually all must have their batteries replaced (or can fail due to excessively high or low temperatures) -- unless you are a skilled electrical worker (or know one) who can wire the remote thermometer to run off of AC. (My brother is a skilled electrical worker, and he did that for me). He wired it then we hung it on the wall, high enough that the birds could not mess with it -- or on it.
In the 2 and a half years that I've used that remote thermometer in the henhouse, it failed only one time -- when we had a power failure. Since mine has been modified to run on AC, it is subsceptible to power failures. If the power failure had lasted long enough, I would probably have run to
WalMart and bought a battery powered "backup" remote sensor to put in there. But power came back on in a few hours, and so I didn't bother.
But since you reminded me, on the next trip to
WalMart, I think I WILL go ahead and buy a back up, battery powered unit -- just in case we have a power failure in the worst of weather conditions.