Of course, the benefits wouldn’t accrue to the wearer. Google would sell the data (suitably anonymised, of course). And your smartphone already provides a huge amount of detail about you. Song Chaoming, a researcher at Northeastern University in Boston, has been analysing mobile phone records (including which base stations the phone connects to) and has developed an algorithm that can predict – with, he says, 93% accuracy – where its owner is at any time of the day (by triangulating from the strengths of the base station signals; that’s part of how your smartphone is able to show where you are on an onscreen map). He analysed the records of 50,000 people; the accuracy was never below 80%.

When you consider that Chaoming was only doing this in his spare time, and that Google has teams of people whose only task is to develop better algorithms to work out where a phone’s owner is, and what they’re going to do based on their past activity and searches, you realise that if you’re using an Android phone, Google probably knows what you’re going to do before you do.