NEW YORK (CNNMoney) -- It's a ubiquitous feature on landlines that's basically non-existent on mobile phones: Caller ID.

Sure, your smartphone will rummage around in your contacts list and attach names to any incoming phone numbers it can find there, but what we think of as true Caller ID -- the service that displays an incoming caller's name, city and state -- hasn't been available, thanks to a bunch of complicated technical issues.







Until now. On Wednesday, T-Mobile is launching a Caller ID feature that will be a first among the four major carriers in the U.S.

As with landlines, this feature doesn't come free. T-Mobile's optional "Name ID" service will cost customers an extra $3.99 per month.

Once a caller's name and location data is displayed on screen, users can add that information to their contact lists with one click. The system is powered by Cequint, which specializes in caller ID technology and partnered with T-Mobile for its offering.

"It's so simple -- it's not sexy, it's not cool, it's not a video game, but it could be one of the best additions to mobile," says Cequint CEO Rick Hennessey

T-Mobile said Wednesday that its Name ID service is now available "out of the box" on its new Android-powered Samsung Exhibit smartphone. The carrier plans to expand that capability to other devices, including the myTouch 4G Slide, later this month.

Name ID will be available on existing handsets sometime in the future, T-Mobile said.

But one glaring roadblock exists: Verizon Wireless (VZ, Fortune 500) withholds the names of its subscribers. That is, when Verizon customers calls a phone with Caller ID, their names are not displayed. That will also be the case with T-Mobile's Name ID.

The $3.99 per month cost will be included on customers' T-Mobile bills, and Cequint shares in the revenue from the service. Hennessey wouldn't comment further on the financial details.

Cequint accesses name and location information through a database managed by Transaction Network Services (TNS), which bought Cequint last year for $112 million. In 2007, Cequint launched its City ID app, which cost $1.99 to display only the the city and state of incoming calls on cell phones.

T-Mobile is a subsidiary of Deutsche Telekom.