Modern and future readers don’t need to be convinced that technology will improve to magical levels; we’ve seen it happen in our lifetimes, in our children’s. To explain more than absolutely needed is to write for the past, but the dead will not read us.
So I have become pointedly effacing on the subject of gear. I don’t want to say anything not immediately needed for the story to continue. It is enough that a tool acts; the tool itself should be as invisible as a butler, and the action the thing of import.
This is a stylistic choice, a convention, but it is informed by function. What is essential about a phone in a story is its ability to communicate immediately over great distance. When your character is warned about a killer – whether through a message from Hermes, a telegram, a party-line, over a cordless phone or a text with an image, or a newly discovered letter from long ago – the device matters less than the message, and the timing. We don’t care how a phone works, unless your plot has a villainous switchboard operator.
In my last story, my characters wear bracelets, which let them access remote data, take pictures, and display images for personal or group view. I have no interest in explaining further, nor did I write a “bible” in advance thinking through the specifics of the interface. The bracelets just do things, and everyone knows how. The good tool is as invisible as the book we read. What matters what it does. And with a bracelet I didn’t even have the possibility of wasteful putting it in pockets, taking it out of bags. The appeal of technology is its ever-lesser drudgery.
This may be a bit thin for some people. But I think it will get dated far more slowly.