I put in a 3x battery. I can go days if I use the "NoBars" app and make a point of using "airplane mode" a lot.
My phone replaced my watch, GPS, camera, mp3 player, books(e-book reader, kindle software, etc...), playing cards, ...
The extra battery adds a couple ounces, but in the end saved me ounces by replacing a lot of other stuff.
There are lots of navigation/GPS apps to play with.
Although I don't rely on GPS and maps on the device, they can come in handy for various reasons. It can confirm your location should you get off the trail, help find alternate routes and help locate resupply and water locations.
Of course, I don't become dependent on the device, but it's comes in handy.