I think that you can get course following to work with Bluetooth? The phone can just send a notification when it approaches the fork.

Though if you want to use your watch as a primary navigation device, you likely need to use LCD/OLED. eInk is not great for interactive map use, not a great use-case for Pebble.

For backup, I like carrying a Garmin satellite communicator. It has its own offline maps and a way to call for rescue in a pinch.