Smartphones.
If you told someone in 1980 that just three decades later they will have a portable phone, a video phone, a worldwide electronic teletype, a movie player with a 300dpi screen, a color photo and video camera with a flash, a satellite world map, a music player that holds over a hundred LP albums, dictionaries and translation tools for all Earth languages, train and flight schedules updated in real time, a library of books (one of which an illustrated encyclopaedia that exceeds Britannica in volume and, in some areas, in accuracy), plus thousands of free porn channels and video games, all crammed into a single wireless device that fits in your pocket and costs less than $300 -- would they believe you?
I'm no expert on science fiction, but as far as I can tell, the vast majority of sci-fi authors missed this idea -- perhaps because it's too ridiculous to be believable.
Added: What's even more ridiculous for a layman from 30 years ago is that all this amazing stuff is implemented on the basis of a computer, basically a machine that adds or subtracts binary numbers and stores the results in memory. "Eh? A music player that works by adding binary numbers? Are you okay?"
I have to wonder why my parents are so desensitised to these advances. My father was born at the end of WW2, imagine all the things he has seen. Yet when I mention transhuman technologies and there potential impact, I expect excitement, instead at best I get shrugs or denial. I wonder what is going on there?
When attempting to introduce non-rationalists to the ideas of cryonics or Strong AI, it appears that their primary objections tend to be rooted in the absurdity heuristic. They don't believe they inhabit a universe where such weird technologies could actually work. To deal with this, I thought it would be useful to have a cache of examples of technologies that have actually been implemented that did, or ideally, still do, challenge our intuitions about the way the universe works.
The first example that comes to my mind is computers in general; imagine what Ernest Rutherford, let alone Benjamin Franklin, would have thought of a machine that uses electricity to calculate, and do those calculations so fast that they can express nearly anything as calculations. Nothing we know about how the universe works says it shouldn't be possible, indeed it obviously is knowing what we do now, but imagine how weird this would have seemed back when we were just coming to grips with how electricity actually worked.
I suspect there may be better examples to challenge the intuitions of people who've grown up in an age where computers are commonplace though. So does anyone have any to volunteer?