Until our last camping trip, my original thinking on this was to only get the 510 rv $159 2 sensor system since I felt that the main reason of having the system was to avoid damage to the TM.
On our last trip it seems one of the rear brake calipers on our TV got hung up and wore one pad all the way down. I had no indication of the problem until the metal wear sensor on the one pad started making noise. I am hoping that by choosing a TPMS system that monitor both Tv/TM with a pressure/temperature indication/alarm that i can get a heads-up for problems like this before the problem gets serious.
@MudDog, Yes, i am considering ordering another sensor for the spare.
Tim