I'm fascinated by the changes I've experienced (though my grandmother was born in 1889 so she saw cars, planes, space flight in her lifetime!).
The first thing for me that immediately comes to mine is computers - even small, cheap, membrane keyboard ones. As a band director, I had to periodically create phone lists of the students on a typewriter. Invariably there would be an error. Or someone would move in and thus have no room to place them properly in an alphabetical list. Every retype could introduce another error. But with an underpowered computer, I could create that list once, edit as necessary, and do a new printout. I remember the person I worked with and how hard it was to get him to understand this. He kept saying, "But you can make a typo with a computer too." Took awhile for him to understand that making a correction held no risk of making another error elsewhere.
Same benefits for maintaining the music library, inventory, handouts, etc (of course, for some of this you needed a printer but the Imagewriter was quite satisfactory.
But the iPhone was huge. Just some of the things relating to work:
A really good - and very heavy - tuner that covered all 12 semi-tones cost over $2000 early in my career. Then they got portable versions (think portable TV - that is, it wasn't hard to move, but you wouldn't want to move it constantly!) for maybe $250. Then we had even smaller ones (a bit thinner than a Mac mini and maybe half the depth for $150. Finally, pretty tiny ones you could put in your pocket for $25. But the iPhone replaced all of that. And you could get metronomes that were far more flexible in what they could do than hardware metronomes I started with. You could get these apps for free or for a few dollars!
CD player. Band directors get demo CDs all the time and we'll go back to old ones when looking for music possibilities or to play for the class to give them an idea of how the music should sound. Of course, you either had to read through a lot of CD labels/jackets to find the songs or you needed to write them down someplace as you got them to make it a little easier (typed into the computer was better as it allowed searching faster), but you still had to put them individually into the player. Then we got ones that could hold 200 or more CDs and you just entered the number of the one you wanted (but you still needed to create the library list and it sure wasn't portable - such things would be set up in the band room and just stay there). But with the iPhone and computer, I just rip the CD which usually will also get the title. Every demo I ever had all in an iPhone.
I also figured out a way to connect it to a Smart Board system in the classroom so I could show videos from my phone.
MAPS on iOS! I used to spend a lot of time trying to figure out how to get somewhere. I'd even buy county maps in areas where I traveled regularly because they were more detailed than state maps. Good for finding little known shortcuts. Now I just use my phone (or computer) and I get directions too. Some shortcuts you still have to find yourself, but it's all right there on the screen.
I used to buy radios that were supposed to be good at picking up distant AM stations (usually at night when the signal would bounce much further). Now I can get an app that lets you select a large number of radio stations without worrying about getting a signal.
Camera! I used to do 35mm film. Even developed my own pictures (as long as they were black and white which most were back in the day). Now my phone does better pictures plus video!
And much much more.
You have to live awhile to really appreciate the changes. I mean, my grandparents would say things like, "I had to walk 10 miles to school, in the snow, when it was still dark". My generation might say, "I had to get up from my chair to change the channel on my TV, and we only had 3 channels!" Our best "remote control" would to tell our kids to get up and change the channel!