This app was mentioned in 5 comments, with an average of 1.20 upvotes
There's an app called "Sleep Talk Recorder" that activates and records when it senses you talking in your sleep.
It's SO FUNNY to hear yourself, I highly recommend it
Link isn't working.
This is the app https://play.google.com/store/apps/details?id=com.madinsweden.sleeptalk&hl=en_US
There's a timer on it that requires a subscription to get past. Should be an easy enough change but I personally no nothing about coding for phones.