Google has officially released the software development kit (SDK) for its Android 2.0 operating system.

Among the new features are support for multiple email account synchronisation, and full support for Microsoft Exchange, which will be bad news for some developers. Other additions include HTML 5 and Bluetooth 2.1 support, multi-touch control and support for zooming with digital cameras.

A Quick Contact function allows users to click on a photograph and get the option to call, message or email that person.

The graphics processing software has also been boosted to make applications more attractive, and the dictionary has undergone a revamp to allow it to learn frequently used words.

The new SDK includes an emulator so that developers can try out new applications before the official release of the operating system.

"Over the next few months, we expect to see more and more Android devices being released," said Xavier Ducrohet, Android SDK technical lead at Google, in a blog post.

"These devices will be running Android 1.5, 1.6 or 2.0. We are also planning a minor version update of Android 2.0 towards the end of the year, and that will be the last update for 2009."

US telco Verizon will announce a new Droid handset tomorrow running an early version of Android 2.0.