"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Apple Seeds First OS X 10.11.2 El Capitan Beta to Developers
The new beta can be downloaded through the Apple Developer Center and through the Software Update mechanism in the Mac App Store.
It is not known what improvements the second update to OS X El Capitan will bring, but it’s likely to focus on bug fixes, security enhancements, and performance improvements to address issues that have been discovered since the release of OS X 10.11.1. According to Apple's release notes, focus areas for the beta include Graphics, Mail, Wi-Fi, Calendar, USB, Notes, Photos, and Spotlight.