Possibly of interest to some - NYC actually has an official live map in beta. https://map.mta.info/

I don't like some of the UI decisions with where it's currently at, primarily not showing the trains and their directions very prominently (the trains are there if you zoom in, but they're just unlabeled rectangles moving on the lines), but it's a start.

It does do a pretty decent job at showing what services are actually operating right now and what stops they're serving, though.