A new feature for the Wii U's video chat service.
http://www.nintendoworldreport.com/news/32407
It will be possible to draw on the Wii U GamePad during video chat sessions. The drawn images will be displayed over the video feed and will be visible by both players chatting.
This information comes from the latest Nintendo Direct which aired earlier today in Japan. During the event this Wii U feature was showcased by Satoru Iwata when video chatting with Reggie Fils-Aime.