Alongside iOS 9 beta 4, Apple has also seeded the fourth beta of watchOS 2. This comes two weeks after the last release to developers. Right now we’re not sure what’s new with this update, other than some bug fixes. We’ll be sure to update this post are more things are found.
You can update to beta 4 in the Watch app > General > Software update > watchOS 2 beta 4. If you don’t have it yet you can download the profile from the iOS Developer Center.