Apple has released iOS 9.1 beta 4 for registered developers. The new beta is available right now through Apple's iOS Developer Resource Center, alongside an over-the-air download for those with the previous beta installed on a device.
Additionally, Apple has also released Public Beta 4 for members of its Beta Software Program. For those with the previous beta installed, they can grab the update over-the-air right now. Those interested in joining Apple's Beta Software Program can check out its website here.
Not a lot is known about the changes present in iOS 9.1, other than the new emoji characters it will add. It is expected to arrive for iPhones and iPads later this year.