Users can set a password for Recorder Plus.
This password is different from the password which can unlock your iPhone/iPad.
After this password activated, please email it to yourself as a backup.
Every time after the screen is locked or the app is moved to background, the password is needed to use the app.
And you can enable FaceID/TouchID for this feature to make the unlock process more convenient.
If you forget it, nobody (including the tech support of the app) can help you reset it.
The important thing about security is:
Nobody except you can use the app does not mean nobody except you can access the data of the app.
For example: if anyone else want to delete your recordings, they can just delete the app or empty iCloud drive directly without accessing the app.
So the key point of security is making sure you are the only one who can unlock your iPhone/iPad and you are the only one who can access your Apple ID account.