A DIY teleprompter with your phone
Broadcast teleprompters cost a fortune, but the physics is simple to copy. A teleprompter floats text in front of the lens without the camera seeing the screen — and beam-splitter glass does exactly that.
The setup
Lay a tablet or phone screen-up, and mount beam-splitter glass at 45° above it with the lens behind the glass. The text reflects up so you see it floating over the lens, while the camera shoots through the glass and sees only you. The reflection flips text left-to-right, so you turn on mirror mode to read it correctly — the single reason mirror mode exists, and this prompter has it built in. Brackets cost a few dollars; the glass is the only real part.
No glass? No problem
For most talking-head videos you can skip the glass entirely: prop the phone directly under the lens, run the prompter fullscreen with mirror off, and set a narrow width so your eyes barely drift. It is not quite the dead-on eye-line of a beam-splitter, but for a phone video it is invisible to most viewers — and it costs nothing.