The Off-TV and cross-region play update for Monster Hunter 3 Ultimate, which was announced before the games release is now available for both Europe and America.
As per software updates for all Wii U games, it will be detected the next time you decide to play and can also be downloading in the background, however this update is small so we recommend you wait.
To actually activate the off-TV playing feature, head into options from the main menu screen, select Game Settings and finally change the Wii U GamePad option to Type 2 which will mirror the normal TV output also to your GamePad.
Happy Hunting!