> But the first time you've been leaning on that GPS a bit too much, you're out on your own at 10% battery and you don't have a backup, the map and headlamp solution begins to make sense in a very visceral way.

That's the value of having a fallback though. You'd be just as relieved to have a backup battery or phone. (Though 10% isn't that bad if at that point you only use it for stopping and navigating.)