Yahoo is working on a mobile service called oneConnect designed to aggregate contacts and communications around what it calls a "socially connected address book."

The service, due to launch in the second quarter this year, draws information from social-networking sites such as MySpace, instant-messaging services such as Yahoo Messenger or AOL Instant Messenger, and email services including Yahoo Mail and Google's Gmail to build a picture of the mood, location and activities of friends and colleagues.

It also stores details of recent communications with address-book contacts, including instant-messaging and e-mail exchanges. All the information held about a person can be viewed on a "social contact card."

Location data is calculated by GPS in handsets that have it, or deduced from nearby cell tower locations. Users of the service can keep their locations private, or opt to share that information with others.

Combining all the information gathered by the service allows Yahoo to alert users of the service when friends arrive in town, or to let them follow up on unfinished business when colleagues become available.

"I can see all my communications archives so when someone comes up to me, I know whether I answered his last email," said Marco Boerries, executive vice president of Yahoo's Connected Life division.

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