I don't have any figures citations since my knowledge comes from when I used to hang out on Precision Agriculture forums, but it's common and getting more so. As drones get less expensive, it's easy to sit in your den and fly over the fields looking for the areas where you should go out and spray some more, or drive over in your UTV and take a closer look at that "weird spot" on the "back 80."

Farmers are very aware of the benefits of technology (why else would you spend half a million $ on a combine?) and will take it up if they see a benefit.

Very large scale, just not in the exact form GP is describing; instead, farmers drop stationary internet-connected sensors all over their fields, their sampling equipment GPS-tags results from every core sample, and tractors have computer-controlled equipment to feed location and quantity information to chemical dispensers.

See e.g. https://home.agrian.com/what-we-do/ for a company that manages this process.

You should go google and research the numbers yourself.