T-Mobile and Samsung on Tuesday unveiled the new T-Mobile Sidekick 4G by Samsung, a rebirth of T-Mobile’s popular phone and messaging device. The phone was previously announced by T-Mobile USA CEO Philipp Humm at a press breakfast in January. Pricing was not announced; T-Mobile said the device will be available this spring. A Web page for the new device enables users to sign up for more information.

[ad#Google Adsense 300×250 in story]The new Sidekick, manufactured by Samsung, is built on Google’s Android 2.2 operating system. It features a 3.5-inch touch-sensitive display that slides out using a “pop-tilt” hinge to reveal a five-row QWERTY keyboard underneath.

T-Mobile is emphasizing features like “Group Text,” which lets users create and manage group messaging conversations. “Cloud Text” lets users text each other across platforms, between computers and Sidekicks. The device includes Facebook and Twitter applications, and, of course, integrated Google services – Gmail, Google Maps, and access to applications through the google Market.

The original Sidekicks proved particularly popular with teen mobile users, and to help curb teen texting and driving, the Sidekick 4G comes with “DriveSmart,” which provides incoming call and message management while the user is driving, to help avoid distractions. A “DriveSmart Plus” service automatically activates while the Sidekick 4G is in a moving vehicle.

The original Sidekick – originally a mobile communication device called the Danger Hiptop – made a big impact with mobile users when it first came to market earlier in the decade