Well, they've actually done kinetic charging smartphones, but it had a battery and i believe it was extremely expensive.

So if you did that and instead of a battery combined it with a (relatively large) capacitor (or some sort of amazing spring) you could have the iPhone equivalent of a shake and shine flashlight. (One bonus being that there would be absolutely no holes, as it would not be possible to charge it via a wall outlet).

It would be completely impractical, but there wouldn't be a battery, so the battery wouldn't degrade. The alternative storage mechanism might degrade, and who knows what all of the shaking would do to the delicate electronics, likely nothing good.

Anyway, I think it'll catch on. I look forward to watching young people on the train shake their iPhone vigorously before making a silly face and taking a picture of themselves in 10 years time.

Let the user toggle between 1 and 2? Which could be useful for new phones where, even though currently full, you know you won’t be able to charge next.