Yahoo (NSDQ: YHOO) has unveiled an all-in-one social phonebook, lifestream aggregator and location-aware mobile communicator app that will let users let users share and read status updates and do multi-protocol messaging with friends on an array of third-party services. One of Yahoo’s most impressive products in years, oneConnect is centered around an address book that, a little like Google’s (NSDQ: GOOG) Jaiku, shows contacts’ status and recent updates from services including Facebook, Twitter, MySpace, Last.fm and Doppler.

A built-in messaging feature will let users IM contacts who use not just Yahoo Instant Messenger but MSN and other protocols. Conversations are threaded like an iPhone SMS conversation. SMS is built in to the oneConnect IM, too, and the app can switch between protocols (ie. from MSN to SMS) depending on a contact’s availability. It even supports email - and can connect Gmail, Hotmail, AOL (NYSE: TWX), Mail and Microsoft (NSDQ: MSFT) Exchange servers.

A “Pulse” feature shows status and activities from the gamut of third parties. It’s like Plaxo Pulse for mobile. Unfortunately for Zyb, it launched its own “social phonebook” just yesterday. The icing on the cake - users can see fellow oneConnect users’ map locations and proximities thanks to cell and Bluetooth triangulation. The demo showed the exact locations of several Yahoos around the Mobile World Congress venue. A “socially-connected contact card” lists recent communications with individual friends across whichever services. Boerries said users’ location data would be “invisible” to Yahoo itself, however, so don’t expect location-based advertising in the short-term.

All of this, thanks to Yahoo’s scale, may put it at the head of the pack when it comes to socially-enabled mobile communication apps. While the likes of Facebook and MySpace roll out their own mobile apps, oneConnect puts them all in one place - for users of multiple services, it’s a Swiss Army knife. oneConnect - which comes as a widget for Yahoo’s Go app as well as a browser-based version and mobile-specific downloads - is due for release this spring. Yahoo is currently negotiating with operators for carriage deals. With a growing number of such deals in place for its oneSearch web search tool, that shouldn’t be too hard.

Don’t read too much in to the presence of Exchange or MSN - Yahoo’s Connected Life SVP Marco Boerries said Yahoo had worked with DataViz on the connections, rather than Microsoft itself. The Microsoft offer was firmly off-topic. Boerries: “We have made our position clear and I don’t want to go in to it at this point.”