Picked up my ET-73 yesterday and played with it today.
As I suspected, the stated range is really exaggerated if you have to pass the signal through anything but air. I'm doing good to get it to go 50 feet after passing through my floor.
The transmitter alternates display of the two temps. The transmitter, according to the directions included, is water resistant but not water proof. The supplied probes are 2 and 3 feet long respectively.
I installed my probes on my heat exchanger in the basement so that the tips were immediately adjacent to the inlet and outlet ports. I used thermal transfer grease to get a good read of the temp of the water as it comes in and goes out of the HX. When the blower comes on, I can now sit in my recliner and watch the outlet port temp drop around 25 degrees. I can also see the inlet temp drop when the boiler runs low on wood and can no longer maintain the preset boiler temp. I haven't decided yet whether to use the alarms. Probably won't since I don't feel like getting awakened in the middle of the night.... but I might set the high limit to warn me of an over-temp (runaway) and I do have the option to set the low limit to let me know the fire is low.
I'll have to play with it....
If you'd like to see pics of what I did, I'll try and post some tomorrow.
Steve