What gives away that someone is reading from a teleprompter?

I'm launching Orate here on 29 September. It's a phone teleprompter, and I built it around one thing I kept noticing: in most teleprompter videos you can tell the person is reading. Their eyes drift down the screen and snap back at the end of each line.

Orate keeps the script in a narrow band right under the front camera, so your eyes barely move from the lens. It also keeps your take if the app dies mid-recording.

Before launch I'd like to hear from people who record to camera:

1. What gives it away for you when someone is reading?

2. Have you ever lost a take to a crash or a phone call, and what did you do about it?

3. Do you rehearse the script first, or read it cold?

I'll read every reply, and anything useful goes into the app.