Yeah if both consoles are modded, you can use a Homebrew app called NTRView on Wii U and the Rosalina Menu on 3DS to use the 3DS's buttons and touchscreen to control the Wii U but the 3DS's touchscreen will be black or show a Homebrew menu. If I'm wrong then sorry but I just saw that nobody replied with an answer and I wanted to help a friend out! :D
Aroma/Aroma Homebrew Discussion
