We have used a Doran 360RV monitor for about two years. We monitor 10 tires (coach & toad). The tire set point pressures are set at the control unit in the coach. There are separate alarms for over-pressure, under-pressure with a slow leak, and a blow-out alarm if the tire pressure drops quickly.
You have to remove the monitor from the valve stem to check or adjust the pressure, but it is no harder than removing a dust cap from the valve stem.
Metal valve stems would be a good idea. We had a flat on the toad because the extra weight of the monitor caused a valve stem to leak at highway speeds.