It looks a lot like the system that was in my 1999 Corvette. The sensors simply radio the information to a central computer. Except in the Corvette, the system was already built-in, so there was no "stand up" display.
I think the GM system is unable to tell you what the pressure is...instead, it measures the PSI "change" from the initial calibration, then displays the "derived" value for you.
That's not necessarily bad, but it's important to know, because whenever you change or rotate the tires, you'll probably have to recalibrate the sensors to...
A) Tell the computer which of the four corners each sensor is at
..and..
B) Tell the computer what the initial pressure is in each tire
...so if I'm right, you'll still need an accurate tire pressure guage.