AirTraffic App/Online Stream: How hard would this be to build?

I have a few air traffic apps where you can see what planes are overhead and, when you click on them, it will tell you what type of aircraft they are, altitude, etc.. I was thinking it’d be a neat service would be is when one was close to you, it was automatically selected and a pop-up would tell you all of that information. You could maybe cast it to a TV, to have on in the background, or make it all happen just on the app. Basically like those others but it gives you that info. automatically. Like I said above, how difficult would this be to build? Perhaps it’s a better idea for one of those existing apps to add that feature. Thoughts? Btw, it is surprisingly interesting if you haven’t IDed planes from your backyard.