We've had applications to sync into Google Calendar for a while, notably GooSync. But Google just released an official set of Contacts APIs (hooks for programmers to use), meaning that full sync into this part of Google may be on the horizon. But, as the Google OS blog notes, the APIs link into a generic contact store and not necessarily a GMail contact set, meaning that there's probably some tweaking at the Google end set to happen in the future, to simplify contact handling.

Watch this space!