Found this video from a channel I subscribed to for Xenoblade music remixes.
Probably nothing but I thought I'd share.
https://www.youtube.com/watch?v=1_6rMa9_UvQ
Essentially haptic feedback, but watch the video to get the details.
http://www.miraisens.com
IIRC the whole haptics rumour started back in the Geno rumour days and that stuff was wrong. Though I think Nintendo could have had that HDMI dongle thing at some point since the dock jsut seems like a plastic box with a fan in it.
In any case maybe some people will find this interesting.