The Apple Watch will make driving safer for HoH and deaf drivers. No more constantly checking the GPS for the next turn because the sound alerts can't be heard. The watch notifies you by tapping your wrist.
http://www.cultofmac.com/320234/how-to-navigate-using-only-your-apple-watch/
How to navigate using only your Apple Watch
Apple Watch will let you know when to turn with haptic feedback: taps. “A steady series of 12 taps means turn right at the intersection you’re approaching; three pairs of two taps means turn left,” says the Apple Watch user manual.
When you get close, you’ll feel a vibration when you’re on the last leg of the route, and once again when you arrive. More...