I bought a remote thermometer because I wanted to see what really happens in the GH when the heater is blowing LOL. The one I have has one sensor (I have one arriving today that supports an additional 3). I put the single one in the very front corner of the GH farthest away from the heater. We had out 2nd frost last night, it was 31F this morning...and I kept my eye on it before I went to bed when we were falling through the 40's and eyeballed it at 0630 this morning. I have the heater set on 60F, and the temp last night never fell below 52 up in the farthest corner. This morning when it was 31 it was 54. I am glad to know that the heater is keeping everything up in the 'outer reaches' that warm.

It will be interesting to see what the temps are in the more central locations where the path of the warm air actually flowers more.

What thermometer did you get?

I need to find one that will record lows(highs) that isn't overly fancy and expensive.

What method are you using to heat your greenhouse and how big is it?

Who me?? Oh yeah me! I have a 1730 sq ft greenhouse with a 200,000BTU propane heater.
I ended up getting one that has 4 sensors I placed around the place that I can see where colder pockets are. It ended up my GH was within the proscribed 330 ft for the Wi Fi to work

Make sure it also has a hygrometer.

It does!