The NPE Runn does indeed produce inclination data, together with speed and cadence. It is quite precise, and sensitive. If I turn it on it’s head, it says 180 degrees… 
I can read the data with an accompanying app. You can also calibrate it to your mill. I find the inclination more off than speed on my unit.
Mind you, I’m not saying the inclination stated at the upper right corner derives from the NPE. I think that is the current inclination that the course has. But what I am wondering about, is the color change. Why does the color change when the number doesn’t? And here is where I’m suspecting and would like a confirmation - that when the inclination reported from the NPE doesn’t match the course, the color indicates that it is off, and possibly also with different colors, if it is way off or just slightly off.
But, I can’t find anywhere where it explicitly says and describes what these indications actually are. So I was hoping a Zwift official could comment. Or point me to a user guide… 