This may sound strange coming from a professional iOS developer but:

Why is this not a website is the most important question of our time.

@kp

Come live in Montana, walk outside past your wifi… and see how that works out for you.

Anything not in a flat part of town or the highway is a big ol’ “SOS” for cell coverage.

(Wyoming was the same way when I lived there)

@philsplace Not letting you do anything meaningful/at all while you’re offline is a big reason to ask this question, and sadly there is no shortage of such apps.
And that’s not even including the cases where you have slow internet, which browsers tend to handle just fine, whereas over-zealous native devs typically err on the low side by an order of magnitude when setting network timeout policies for their app.
@kp