The Sidekick Is Dead. Long Live the Sidekick. T-Mobile Aims to Reinvent the Original Smartphone.

Just a couple weeks after announcing plans to kill off the old Danger-based Sidekick service, T-Mobile is ready with some details on its first Android-based model.

The Sidekick 4G, which looks a whole lot like the Sidekicks of old, is being made by Samsung and should be out “later this spring.” Unlike the Danger-based models, though, this Sidekick has a touch screen. Plus, since it is Android inside, there are access to all the usual apps and services that one would expect. T-Mobile didn’t announce how much people can expect to pay for the new Sidekick.

Although the T-Mobile’s support of the Danger-based Sidekicks has been waning for years–and dropped precipitously after a major server failure in 2009, the company said the brand has remained strong and kept a loyal following.

“It was kind of a no-brainer for us to bring it back,” said Joe Fernandez, the product manager for the new Sidekick.

T-Mobile said it spent a long time researching what attributes defined the Sidekick as well as which of its quirks were just a bit too quirky. As with past Sidekicks, the device features a unique pop-open screen and large five-line Qwerty keyboard. Also retained, though tweaked a bit for Android is the dedicated “jump” button for moving between applications. Out, though, is the color-changing mood-light scroll wheel that cycled through different colors when a call came in.

As with past Sidekicks, a key feature is the device’s messaging capabilities. While early Sidekicks focused on instant messaging, this time around, the focus is on social networks and text messaging–including built-in Twitter and Facebook connections and group text messaging added to the main texting program. Although this Sidekick has far fewer cloud services than the Danger-based models, T-Mobile does plan to offer a program for viewing and sending text messages on the Web.

From a hardware perspective, the Sidekick 4G is similar to Samsung’s Galaxy S models, paking a 1GHz Samsung Hummingbird processor along with a front-facing VGA camera for video chat and a 3 megapixel rear camera. (For those that can remember all the way back to the original Sidekick, it had no built-in camera and an optional camera attachment could create photos about the size of a postage stamp.) The interface is similar to Samsung’s TouchWiz Android UI, but has some Sidekick-specific tweaks including keyboard shortcuts, custom ringtones and wallpapers.

T-Mobile is clearly aiming at the same younger demographic as were targeted by earlier Sidekicks, albeit with different features and services than in the past. In addition to building in apps for Twitter and Facebook, the Sidekick 4G has a means for updating social network status right from the notification screen and also integrates social contacts into the address book. The Sidekick will come in two colors, black and a pearl magenta and T-Mobile said it was too soon to say if this would be only the first in a new family of devices. Rather, T-Mobile said it wants to see how this initial Android model does before committing to future products.

The Sidekick 4G will also include T-Mobile’s DriveSmart and optional DriveSmart Plus software aimed at discouraging users from accessing their phones while driving.

While T-Mobile won’t guarantee it, officials say the company is hoping to have the Sidekick 4G ready for customers before it flips the lights off on the Danger servers at the end of May.

Below is a photo timeline of T-Mobile’s Sidekick line from the original black and white model from 2002 through the new 4G Android device announced on Monday. (Special thanks to ATD intern Erik Silk for putting this slideshow together.)