What is something that's crazier than the wildest dreams of any ~1970s nerd, but exists today? I'll start with an easy one:

Cameras in general. Good quality film cameras took some work and were heavy. Like bookbag heavy. You’d have to carry a little set of filters (thin lens caps that screwed onto the main lens) in addition to another lens or two to get a good range of options. Now, tap, done. Copies? NP. Black and white? Tap. No need to use up the roll of color film and then switch to black and white film.