"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Apple Seeds First OS X 10.10.2 Yosemite Beta to Developers [Updated]
The new beta, build 14C68k, is available through the Software Update mechanism in the Mac App Store and should be available in the Mac Dev Center soon. The beta also includes Safari 8.0.2 and an update to the Mail app (version 8.2).
Like OS X 10.10.1, as a minor update, OS X 10.10.2 is likely to bring bug fixes and performance improvements to the operating system. OS X 10.10.1 introduced several reliability enhancements, including improvements to Wi-Fi, but many users have still been reporting issues with Wi-Fi stability in Yosemite.
Update: It appears that OS X 10.10.2 is causing the latest version of Google's Chrome browser to crash. Retina iMac owners are also seeing display issues with the beta.
Update 2: The Chrome/10.10.2 issue is related to the trackpad, and the crashing can be circumvented by using an external mouse and disabling the trackpad while the mouse is plugged in.