Apple has just seeded the third-iteration of iOS 8 with build number 12a4318c to registered iOS developers via the Apple Developer Program. Apple unveiled iOS 8 at the WWDC 2014 Keynote with numerous new features and improvements including interactive notifications, widgets, support for third-party keyboards, Handoff and more.

The new iOS 8 beta update is now available for download on iPhone, iPad and iPod Touch via online developer portal as well as via Over-The-Air (OTA) update.
List of Compatible Devices
iOS 8 beta 3 is compatible with the following iOS devices:

• iPhone 5s, iPhone 5c, iPhone 5, iPhone 4S
• iPad Air, Retina iPad mini, iPad 4, iPad mini, iPad 3, iPad 2
• 5th generation iPod touch

New Features in iOS 8 Beta 3
Here is a brief description of the latest features ported to third beta iteration of iOS 8 (courtesy of iPhone Hacks):

• iCloud Drive: iCloud Drive app gets a new welcome screen.
• App Analytics: A new opt-in screen allows sharing iOS crash data and other analytics information with developers.
• Handoff: A new Handoff toggle is available via Settings > General. You can enable this option to effortlessly switch between your Mac, iPhone and iPad without dirupting your work flow.
• QuickType: Enable or disable QuickType via new toggle setting in iOS 8's new keyboard feature that predicts words for user input based on current context.
• Messages: New option in Messages app automatically preserves video and audio messages following the periodic maintenance, as messages by default get purged after some specified time.
• Notification Center: New UI for clearing notifications.
• Wi-Fi Calling: iOS 8 beta 3 introduces new Wi-Fi calling feature to enable making phone calls over Wi-Fi. Users can avail this feature via carrier support with T-Mobile being the first to add this feature.
• Camera App: The native camera app now shows how many days left until a photo is deleted via Recently Deleted section.
• Wallpapers: iOS' default wallpaper gallery gets new wallpapers for iPhone and iPad.
• Weather App: Weather app is redesigned with tweaked UI wherein the details at the bottom are horizontally centred instead of having two separate columns like in previous design.
• Find my iPhone: New enhanced version of Find my iPhone and Find my Friends app allows you to move your friend list to an iCloud account.