So, as a note, there are approach and departure frequencies listed for major airports in the airports com list. For example, KSEA, KLAX, KABQ all have a multitude of frequencies, and they each have a narriative that tells you what sector to use them in.
We don't show the "child" airports of these yet, where a underlying airport will list KSEA's approach/departure in its own list.
We don't actually know how to show TRACON frequencies by position, only via an airport lookup. If you know of any product that allows you to just take an aircraft position and show you the correct TRACON, we'd be interested to know so we can research it.
The other issue is ARTCC frequencies. These are on the list to put in SkyView as well, and these can be looked up by "nearest", but no other way. So which is the one that people are most interested in?