sometimes audio is not enough, e.g. when driving motorbike/scooter in big city (Bangkok, Kuala Lumpur) audio navigation is not enough to on time figure out which lane ramp you have to use at some intersection.

For motorbikes there are already options to get a HUD in the helmet, i.e. a CrossHelmet or Argon Transform.

This is not an endorsement of these products, I have no idea if they are actually any good.