One good example of “simple and non-invasive as possible so it becomes part of the fabric of everyday life” and “most personal computing that’s ever existed fit comfortably like a second skin” is the Hexoskin smart shirt (http://www.hexoskin.com)
It’s completely open data so any wearable manufacturer can use or display the raw data (256 times per second) generated by Hexoskin thanks to an existing API.
Hexoskin has been on the market since Q4 2013.
Sorry if this looks like advertising, when reading this paper I just felt that our product answered a few of the questions raised, so I thought I should add my 2 cents!