The Pressure Pro system alerts loss of signal in about 15 minutes.
The sensors on most systems sends a pressure and other data about every 5 minutes. (note this is routine data and not alarm data such as low pressure. That is sent by most systems in 5 seconds or less.)
As such a loss of signal would take at least 10 minutes before the receiver could be sure it has lost communication with a sensor.
The Pressure Pro has an additional useful feature during setup of the system. You can get signal strength of each sensor. If you have a sensor with a low signal strength then a repeater or external antenna may be needed. Also with the signal strength you can experiment where the best location of the repeater and antenna should be.
I found I could not find a location that was suitable with a repeater. Pressure Pro allowed me to return the repeater and supplied the external antenna which gave me good signals from all 10 of my sensors.