Um Beeper, support
Um Beeper listens while you talk and beeps each time you hesitate, um, uh and er in English, euh in French, so you hear your filler words the moment they happen. It works offline, with no account, and everything stays on the iPhone. It is called Euh Beeper in French.
Getting help
Write to contacttheomartin@gmail.com. I built the app and I read every message myself, though there is only one of me and the answer is not always the same day. Your iPhone model, your iOS version and what you were doing make a problem fixable on the first reply.
Worth knowing before you write
It misses some ums and beeps at the wrong time now and then. A drawn out um is caught within about a fifth of a second, a very short one can slip through, and a similar sound can set it off. The sensitivity slider in settings trades one for the other: to the left, more beeps, to the right, fewer false alarms.
The False beep and Missed um buttons save the last three seconds of audio in the Files app, under On My iPhone. Sending me those clips is the most useful thing you can do for the next version.
Beep or vibration. If the sound bothers you or the people around you, turn the beep off in settings and keep the vibration.
It keeps listening with the screen locked, until you tap the button again. iOS shows the orange microphone indicator the whole time.
Nothing is on a server, so there is no account to recover and no history to restore on a new phone. Deleting the app deletes your recordings.