While playing around within the settings last night, I ended up within Accessibility Settings and was looking for stuff I haven't seen before. Turned on "Switch Control" to see what it was.... it was a nightmare. It cycles between red boxes on your screen and when you tap on your screen anywhere it selects that box.
To give you an idea. If you are on your home screen, it will first highlight the first row of apps as a whole and then the next row and so on. Then when you click anywhere on the screen it will pick that selected row and then cycle the individual app icons. It cycles at about .5 second increments so its annoying to select the correct one.
But say you go to turn this thing back off, you have to make it all the way back to the accessibility settings and then figure out how to scroll down because the Switch Control setting is near the bottom. While its cycling you have to double tap on the bottom half of the screen (atleast thats how I got it to come up 2 out of the 10 tries, it will usually just select back and kick you out of the accessibility settings since it selects the first button when you double tap sometimes).. I finally got it to select Auto Scroll and was able to turn it off after about 45 minutes of trying....
You have been warned. or you have a terrible prank to play on someone.
TL DR: Do not turn on Switch Control.