Hello, in this case, I use only the temperature probes to monitor the engine. It is a way for me to check if my engine is too lean or not.
I have understood the optimal temperature is near 90°C (194°F). Up to now, I reach 70°C (158°F) with the medium needle e at 3/4 opened, and the high speed needle at 1 1/4 opened.
Regarding the other probes: before I tried a GPS sensor just for fun (speed and altitude), but it died in flight...
And on my last electric helicopters, I had a current probe to monitor the BEC of my ESC, in order to be sure of its capacities to provide a good level of current.
But after the adjustment phasis, there is no more interest to keep them.