Midi keyboards and controllers for some direct playing and composing are the most obvious ones. But there will be more out of the box thinking when this comes into full swing. I am looking forward to when this is an actuality and it seems that the development is far ahead so it could be not too far of into the future.
One thing that suddenly makes smart watches interesting for music making is when this gets implemented. I have really been wondering what real uses smart watches are bringing to the table but now...
To read more:
http://mashable.com/2015/05/30/google-project-soli-analysis/?utm_cid=mash-com-Tw-main-link