Apple has just released the fourth beta version of iOS 8.2 for software developers and others who have signed up to participate in the iOS 8 beta program. The over-the-air update should also be available from the Apple Developer Center.
To download the update over the air, simply go to Settings > General > Software Update on a device already taking part in the beta process for iOS 8.2. There's no word yet on what beta 5 contains, other than bug fixes and improvements. iOS 8.2 includes the WatchKit SDK, which will allow developers to make apps that will work on the upcoming Apple Watch.