Google's Gmail product manager Jeff Ellingson noted the new support for CardDAV in a blog posting today.
The new support requires iOS 5 or higher, and currently requires users to manually set up an "other" CardDAV account, as Apple's automated setup for Google accounts on both OS X and iOS only configure Gmail & Notes (via IMAP), Calendar & Reminders (via CalDAV), and Messages (via XMPP).
In the future, Apple will likely add support for simply checking a box for Contacts sync to simplify CardDAV account configuration, just as it does for Yahoo and Facebook accounts that already support CardDAV.
Apple pioneered support for the CalDAV and CardDAV open specifications in its efforts to build open Calendar and Contact sharing services in OS X Server as an alternative to Microsoft Exchange Server, which uses proprietary protocols to sync such data between clients and servers.
The company first added CalDAV and CardDAV support to its mobile devices in iOS 4 two years ago.
Apple has aggressively pushed both open standards for calendar and contact sync, enabling users to seamlessly use Macs and iOS devices with not just its own OS X Server and iCloud offerings, but also third party services from AOL, Google, Yahoo and any other systems that support them.
CalDAV and CardDAV are based upon the WebDAV specification for building web servers capable of both reading and writing information, so implementing the protocols is relatively simple for third parties.