'Apple TV Software beta 4' is available for the latest 3rd generation Apple TVs (1080p), since Apple dropped support for the 2nd generation 720p version with iOS 8.
This pre-release version of Apple TV Software includes support for Family Sharing and can be used for testing AirPlay and HomeKit with your iOS apps.
There have been some rumors pointing to possible Continuity integration with the Apple TV, but Apple has yet to announce anything officially.
Let us know if you spot any major new changes in this fourth beta seed! Be sure to follow iClarified on Twitter, Facebook, Google+, or RSS for updates.