Mad scientist Brett Terpstra on his excellent Marked application as a teleprompter:
Once you have the theme, you can start prompting just by hitting the ‘s’ key in a Marked preview. That will start autoscroll at the slowest speed. Use left and right arrows to speed up/slow down the scroll speed. (You can also click and drag on the meter that appears in the lower left of the screen.) That’s all there is to it.
If you’ve ever made the jump from writing a how-to to recording one, you know how hard it is to narrate what you’re doing on screen. Marked is a neat tool but this is just next-level cool.