This app was mentioned in 4 comments, with an average of 2.50 upvotes
I've used the audio book trick for a couple of years now and have been listening to the Discworld series (narrated by Stephen Briggs and Nigel Plainer). They are both great narrators and there are so many books that by the time you run out you'll have no problem starting over. I do recommend that you use a player with a timeout function (I originally used Audiobook Player 2 before buying Listen Audiobook Player, both on Android) so you can give the player a slight nudge if you're still awake, or have it fade out and pause if you're asleep.
That said, I'm not really relying on audiobooks lately. Found out that my sleeping issues where stress related, and since changing a few things I've had a far easier time falling asleep.
Not pebble related, but Audio Book Player 2 does almost this. It detects lack of movement and pauses when it has been still for a set time. Works really well.
I have used this one for years. I listen every night going to sleep. https://play.google.com/store/apps/details?id=com.frma.audioBookPlayer2
https://play.google.com/store/apps/details?id=com.frma.audioBookPlayer2
This one has been my go to since I got my first android phone. Simple to use and has a great sleep function