I'll give you the heads up!
It's a Head Up Display

Nah seriously it normally requires a tinted sticker to be place on the windscreen.
These I found distracting in the day time period. At night you don't notice it.
Once I calibrated my speedo with a Tech 2 and switch my VY dash into Police Mode to get the digital speedo I flicked the GPS HUD.

I suppose it depends on the car and situation. You can purchase GPS HUD units from about $70.