That'd be so neat to use the PS Vita with GT.
It could display real time data (position, lap time, tire status...) on the portable screen so we could enjoy the display on our tv without any information but still keep track of precious data.
For those playing with the external view, the Vita could be used as a mirror.
Even better, we could stream the game à la Wii U from the PS3 and keep playing on the Vita screen even if the tv is turned off.