When I was at school - some 40 years ago now - I recall reading a science fiction story in which at one point the boy protagonist meets a visitor from the future (or maybe just another planet) and the thing that really struck me then was the description of how he operated his "devices".

The author described how the visitor had a very small device in his hands, and made tiny movements to manipulate the device - which both the protagonist and I found remarkable. ( This was a time when radios, tvs and phones sat on the shelves and had big dials etc. )

Now that this has basically come true, I'd love to be able to re-read that.

I know it's not much to go on... but... anything?

I was into Clarke, Asimov and the likes at the time.