How accurate is the oil pressure reading on the ultraguage em?

 

Since there is no sensor from the Rover factory, how would Ultra Gauge get an oil PSI reading? I thought it read live data from the OBDII port?

Now coolant temp, there's a sensor. Would assume it can do voltage, since OBDII port has a 12 volt power wire. RPM, vehicle spped, various other sensors. But if you can't see it with your code scanner, does Ultra Gauge have an auxillary input to add an electric gauge sender unit?