Personally I think smartphones will never be good at known-goal interaction. They're general-purpose devices with a hilariously low-throughput interface that need to accommodate low-tech users. You're always going to have to navigate a bunch of screens to get to any given function because the real estate is so small.

Could apps be better? Sure. Can any app get as good as a button that's already right there when you realize you need a replacement? I don't see how.