Google finally brought push for Gmail to the iPhone and iTouch through Google Sync. Using Google Sync , you can sync calendars and contacts wirelessly and also receive Gmail emails once they hit your inbox.
All this can be done via the native Mail application, which will include options for synchronizing contacts and calendars as well. To configure your device, just follow this guide that allows you to make best use of the service.Below your have an overview of Google Sync for Mobile. Provides two-way contacts and calender synchronization for many mobile devices.