The badges you earn on one device from an Audible app sync between devices (like when I listen from my iPad at night vs. my iPhone in the car).
There are three different levels of badges you can obtain: silver, gold, and platinum.
Complete an Audible book that is longer than 24 hours long. (Infinite Jest did the trick for me!)
Look at your profile page and badge page and switch back (in and out) over 50 times to obtain the Watchtower badge.
Read in at least 2 books in the course of any consecutive 7 day period.
Listen to an audible book for at least a total of 10 hours on a weekend.
Listen to any selection of books for a course of at least 8 hours on any given night.
Listen to the same book 3 or more times in a given day or week.
Listen to books on any 7 consecutive days.
Read a book for at least 3 hours during a lunchtime stretch between 11am and 3pm.
Complete an entire book in one session.
Listen to an Audible book for at least 2 consecutive hours in a day.
Listen to 3 book titles in one day.
Have at least 50 Audible audio-books in your library.
Share your badge progress 5 times on Twitter and Facebook.
Place 10 bookmarks in a single book.
Dabbler (the only one I don't have yet):
I messaged Audible about this and they said they discontinued this badge. I don't know why it still appears in the badge collection at this point.