Google Maps has supported on-the-route searching for a while - it will give you a bunch of options on the map, indicating how much of a detour each requires.
The UI in my car categorizes points of interest then shows me a list sorted by range. It's a lot easier to parse while driving but the Google Maps functionality is good. Over a long distance I could see it being a bit hard to decipher. I believe my car also allows filtering by top-tier stations only.
I did not notice this functionality because I have learned to be very afraid of touching the screen while navigating with Google Maps for fear that the navigation will be cancelled and I will have to start my search over again.