Many Contact Sensors have internal header allowing you to wire something to them that is either Open or Closed electrically.
I have used this to add a (physical) pressure sensor across the connector, which is largely a resistor... as you apply pressure the resistance lowers, eventually reaching the point where the contact sensor makes a report. I want to be clear that the pressure sensor I'm referencing is effectively Weight, not air pressure. I've used the same thing to connect a Float Valve, to measure when my pool needs filling. It's just a magnetic switch in a stainless steel sealed tube. Yet another is an actual switch, a really big button variety, that I use to turn on an outdoor shower. (I was using the pressure sensor under a bamboo grate, so that when someone stood on the grate, the shower would come on... but the bamboo died in the sun and I went old school the 2nd time with a big ol' button.)
What this means is you have to get your air pressure device you use to offer a switch type contact or a resistance that varies by pressure. Then connect it across the header in the Contact Sensor.
One example. I connected this pressure sensor:
My float Valve:
