Display: 6.2 inch (15.7 cm) 854×480 16:9 @ 158 ppi
Sound: Stereo speakers, Headphones

Input:
Motion sensing
Touchscreen
2 Analog sticks
D-pad
Digital buttons
Microphone
Gyroscope
Accelerometer
Magnetometer
Extension Connector

Camera: Front-facing camera
Touchpad: Single-touch LCD display
Connectivity: Proprietary wireless based on IEEE 802.11n NFC, Infrared
Dimensions: 5.3 inches high x 0.9 inches deep x 10.2 inches wide

The Wii U GamePad is the standard controller used by Nintendo's Wii U video game console. Incorporating traits from tablet devices, the GamePad incorporates both traditional input methods (such as buttons, dual analog sticks, and a D-pad) and a touchscreen. The touchscreen can be used to supplement a game by providing alternate functionality or an asymmetric view of a scenario in a game. With the Off TV Play function, the screen can also be used to play a game strictly on the GamePad screen, without the use of a television display at all. Conversely, non-gaming functions can be assigned to it as well, such as the ability to use it as a television remote.

Source: Wikipedia, "Wii U GamePad", available under the CC-BY-SA License.

Wii U GamePads are region locked. You cannot use a GamePad from a different region with a non-matching region Wii U.