News: Google has unveiled an operating system designed specifically for wearable devices called Android Wear, plus details of the first smartwatches to incorporate the technology.

In a series of Youtube movies released today, Google previewed the Android Wear operating system that will extend apps currently available on Android devices to present contextual information designed to be viewed at-a-glance on wearable devices.

"With a wearable device you can be going about the rest of your day, just glance down at your wrist and the information you need is there right away without even having to ask for it," said Android's director of engineering David Singleton.

Using the existing Google Now service, the new user interface will prioritise information specific to the user's context to allow a more passive experience, without the need to retrieve the information from multiple applications.

For example, in the morning it could show local weather reports, the time of the wearer's first meeting and travel time to get there based on current traffic conditions.

"Watches are good at telling time, but imagine having useful actionable information there precisely when you need it, automatically," said Singleton.

The launch movie also shows a user receiving an alert for jellyfish when about to go surfing, and immediately swiping to a screen showing other beaches in the area to head towards.

"Think about the times you need information most urgently," said Android designer Alex Faaborg. "The stuff you care about moves with you from place to place so you never miss out on the important stuff."

Android Wear incorporates voice control and, like Google Glass, will be activated by saying "Okay Google".

"We put a lot of thought into how simple this has to be," he continued. "It has to be incredibly fast, incredibly glanceable. There're really only two components: the information that's most relevant to you and the ability to be able to speak to it and give it a command."

The system will also facilitate receiving and responding to text messages and calls, and listening to music. It could also incorporate health or activity-monitoring functions to rival devices like Nike FuelBand and Fitbit.

The first device announced to use the system, the LG G Watch, will be launched by South Korean firm LG later this year. The two devices shown in the Android Wear launch movies with either a round or square case are reported to variations of the forthcoming Moto 360 from Motorola.

"To bring this vision to life, we're working with consumer electronics manufacturers, chip makers and fashion brands who are committed to fostering an ecosystem of watches in a variety of styles, shapes and sizes," said Singleton.

Google today made a preview software development kit available, so that developers can begin to extend Android applications to work with the new system.