The GamePad has a steel frame, but looks to be all plastic on the outside. It has a directional pad (sadly, it is a circle, which usually offers less accurate input), two analog sticks, four face buttons, and two shoulder triggers. The layout is similar to a PlayStation controller with the analog sticks parallel to each other, rather than an Xbox controller where the sticks are off-set. Oddly, Samsung also decided to rotate the face buttons so they are in more of a square formation rather than a diamond.
The GamePad is a bit smaller than a PlayStation 3 controller, but about the same weight. It is designed to sock a smartphone anywhere from 4-inches to 6.3-inches. It should work with any Android device running Android 4.1 or higher with Bluetooth 3.0, but it has (obviously) been optimized to run on a Samsung Galaxy device running Android 4.3 or higher. Interestingly, you can even use AllShare Screen Mirroring through an HDMI cable to play games on your TV.
There is also a companion Samsung Mobile Console app, which will launch with 35 games including Need for Speed: Most Wanted, Asphalt8: Airborne, Modern Combat 4: Zero Hour, Virtua Tennis Challenge, and Prince of Persia: The Shadow and the Flame. Samsung is promising "much more" in 2014.
The GamePad and app are available now in select European markets, and Samsung says it will be coming to additional regions in the coming weeks. No word on pricing.