I have a HUD for my speed (), but I would really like to have my GPS as a HUD too. Simply reversing the screen display and placing it on the dash isn't enough as the back-light is too dim to project much of an image. Also, a HUD GPS could just be an arrow head indicating the direction of travel. This might lend itself to being built from a charlieplexed LED matrix kit for Arduino. So, my challenge for Ben is a HUD GPS.
