Google has announed availability of a new version of Google Sync, which includes beta support for two-way sync support for the iPod touch and iPhone. Users of either of these devices can send their calendar and contact updates to their Google account and have these changes distributed to all the devices syncing with that account. They can also, in turn, make changes in their Google account, and these changes will be pushed out to the mobile devices.
This syncing feature works because Google has licensed Microsoft's Exchange ActiveSync protocol to push the information fairly quickly, usually within minutes, to either of Apple's handheld mobile devices or your Google account. It works only with on your iPhone or iPod touch running firmware version 2.2. Google Sync will not work on the iPhone or iPod Touch until you've enabled the syncing of Google Contacts in iTunes and setup an Exchange account on either of these devices.
The beta is not without limits; it will not currently sync email and there is a limit placed on the number of calendars or contacts that can be synced. Another very important aspect of the beta is that Google recommends that you back up all your local data on your mobile devices before using Google Sync. Instructions for backing up your data are here for Mac or PC.
The service could be seen as a direct competitor to Apple's MobileMe service; Push services provided by ActiveSync would make Google an attractive alternative to MobileMe.
It is highly recommended that you completely read all of the information on Google Syncs website before using this beta. As the site states:
Important! Google Sync uses the Microsoft© Exchange ActiveSync protocol. When setting up a new Exchange ActiveSync account on your iPhone, all existing Contacts and Calendar events will be removed from your phone. Please make sure to back up any important data before you set up Google Sync.
You can see a video about Google Sync below.