Teleprompt+ has been around for awhile for iOS, and developers Bombing Brain just released a version for the Mac.
Launching the program gives you a two-panel window with one side showing your scripts and the other your work area where you can type out your main speech, then use the menu on the right to adjust settings or add cue points. The settings are pretty robust and control the speed of the teleprompting, countdown, timers, font and whether or not you want to be guided. What the software lacks is the ability to have your speech text one color and your cue points another. The cues quickly get lost among the regular text when the prompter is on.
When the teleprompter is activated, you can use your mouse, keyboard, gestures on a trackpad or an iOS device (via the free Teleprompt+ remote) to control the prompter. You can pause it mid-speech, speed up or slow down. Four sets of timers show you how long your speech is expected to take, how much time remains and how long you actually took to do your speech.
Teleprompt+ is $19.99 on the Mac App Store, and it's a great program to have if you plan to give a speech.