Google has demoed its "nearly completed" mobile operating system at the company's annual developer conference in San Francisco.

The shows and tell session is being described as the most extensive public look so far at the Android open source platform.

On display to the 3000 plus attendees was a way to unlock phones by drawing a specific shape on the touchscreen instead of entering a password and bookmarks for favourite sites on the device's home page.

In addition a "compass" tool that automatically roams with the phone while a user looks at photographic images of a city map, a magnifying tool to zoom in on web content and a mobile version of the video game "Pac Man" were demoed.

The new features were shown off on an unidentified touchscreen device, although some reports suggest it was HTC's "Dream" handset, said to be the prototype used to convince companies to join the Open Handset Alliance some 7 or so months ago.

The Google representative showing the system would not confirm exact dates for the platform's launch, just that Android will hit the market some time during the final 6 months of this year.