A little surprised that Backpacker magazine didn't pick their own mapping app -- the Trimble-based GPS Trails Pro -- but this is a solid list. I think the outdoors is really a great place for virtual reality apps in particular!

Is it hard to access 3G and/or LTE from most hiking trails these days?

COOL!  I would also add that you can use the sunrise/sunset feature on Google calendar too.

I did not even realize Google calendar had that feature! Cool...