Smart devices since iPhone had been lacking so far
I think that iPhone hasn't yet been superseded in terms of how big of a jump or shift it introduced toward smart devices.
Most of the later attempts have been lackluster. Voice assistants stand out as shining examples. After 10+ years of their existence, I'd summarize voice assistants as “A whole lot of fancy UI with nothing of substance behind it”.
With LLMs, we are at another iPhone-style inflection point. LLMs have already far surpassed whatever little capability was behind the voice assistants. We now have a very compelling capability, currently being fronted by basic low-level UIs. Soon we'll have small portal personal LLM devices.
Maybe something similar to what Humane Pin was attempting. A very successful and striking example, although fictional, would be from the film Her.