I'm actually not sure about the "one big touchscreen" idea - it's seems likely some designer considered it, but even Star Trek TNG PADDs had more than one touch display segment.

Portable radio-type devices have been all over, portable computers as well, and networking radios autonomously together made appearances. Ditto for adding a camera to standard communications devices. I'm not really sure how much of it you need going at once to consider it a smartphone.

Like the guy in the link mentions, what people would choose to do with them and just how often was the hard thing to predict. When someone pops open a version of the internet in Heinlein it's always to do research. It's never cat pictures or porn or to post a random picture of themselves and what they're doing. Usually the computer is part of your spaceship or whatever, not in your pocket, just for that reason.