I've seen folks put indoor/out door thermometers outside the rig to keep track of the temp for their pets.
I've seen folks put them in their utility bay to monitor the temp during cold weather.
I've seen folks put them in the fridge/freezer to monitor that temp.
You can normally have three measuring three different things (most have an A, B & C frequency) if you are not too close to your neighbors.
Many times in commercial RV parks, and rallys, I don't need to put my outside thermometer up because someone close is using one, and I can read their signal.