Even a Garmin from 5 years ago works great with voice commands and great displays. Of course we have iPhones and Galaxys that do that too, no need for extra gadgets
It doesn't matter where it's displayed, looking at a map while driving takes attention away from the road.
In the days of paper maps everyone knew it was silly and dangerous to try to unfold and read one while driving. I don't know how this common sense has disappeared just because of LCD screens.
A HUD does steal from outward-facing attention. It's ok in aircraft because the forward environment for aircraft is far less cluttered than for a car. That's also why self-driving cars are so much harder to do well than self-flying aircraft.
Which makes sense since your eye does have to look away from the road in order to use the device. Not to mention the drop in attention.
Also have you heard of sat nav ?