What's the most in-demand API on the web that hasn't existed until today? Wether they knew it or not, millions of people online have thought to themselves "why is this new site I'm on asking me for my Gmail username and password? When will there be a secure API for me to pass those contacts allong without giving up my password?"

That day has come. The Google Contacts API went live tonight and it enables far more than just contact transfer.

According to the Contacts API site, the new API allows application developers to enable their users to:

  • Synchronize Google contacts with contacts on a mobile device
  • Maintain relationships between people in social applications
  • Give users the ability to communicate directly with their friends from external applications using phone, email, and IM

"The Contacts API allows developers to create, read, update, and delete contacts using the Google Data protocol, based on AtomPub," the announcement says. "It also allows for incremental sync by supporting the 'updated-min' and 'showdeleted' parameters."

Pretty hot read/write stuff and particularly interesting given today's developer launch of the location tracking Fire Eagle from Yahoo!

One thing Fire Eagle has going for it that the Google Contacts API does not is support for the open authentication standard oAuth. Support by Google for oAuth in this API would have reduced the work required for developers by allowing code from other authentication proccesses to be reused. Google is supporting oAuth in OpenSocial, but on some days that hairball is harder to get excited about that a nice simple API like this one that delivers clear value.

Today's a big day for developers, may the secure Gmail contact leveraging begin!