Talk2Camera
Export and publish

Export subtitles as .srt

A separate subtitle file for platforms that want one, instead of burning the words into the picture.

iOSAvailableAndroidAvailable
The Captions tab: a Burn in captions switch, a note that timings are estimated from the script, an Adjust timing button and an Export .srt button.
Captions are built from the script you read, and the app says plainly when the timings are estimated rather than measured.