Helsinki-based Jaiku is a social networking and mini-messaging service that enables people on the move to keep track of each others'' activities using curt missives sent to mobile telephones.

Jaiku describes the service as one that lets users share their "activity streams," which it defines as "a log of everyday things as they happen." An activity stream can include recommendations, details of events the user is attending, photos and questions. Users can post new items online, via instant message and on mobile phones using text message.

Jaiku also offers a mobile feature that allows users to view items posted by friends in the list of contacts on their phones. Mobile users can also opt to share availability status, location and calendar items with anyone else or with selected contacts. The capabilities are available for users of Nokia phones running Series 60 software.

"Technology has made staying in touch with your friends and family both easier and harder," Google product manager Tony Hsieh said in web message.

"Living a fast-paced, on-the-go lifestyle is easier (and a lot of fun), but it''s more difficult to keep track of everyone when they''re running around at warp speed. That''s why we''re excited to announce that we''ve acquired Jaiku," he added.

The companies did not disclose terms of the acquisition, which is closed. With the announcement, Jaiku closed new user registration but will still allow existing users to invite friends to join. Current users can sign up for an invitation to participate in the testing of new services to come, Jaiku said on its website.

Google has made several acquisitions over the past years. Recent buys include Postini, Panoramio and YouTube. Google bought mobile social-networking company Zingku Inc. two weeks ago.

Google is also reported to be developing a "gphone" with an open-source software platform tailored to its online services, even as more and more internet users go mobile.