Google Glass. I thought this would become standard, miniaturized, and used in all aspects of life. Perhaps I read Daemon too much, but I was sure Glass would fly
Now that the hype over the original Glass release subsided, there are actually some promising developments for the enterprise market. Notably Augmedix, a company aimed at optimizing doctor-patient interaction uses it as a tool allowing for remote medical assistants (https://www.augmedix.com)
It could have revolutionised journalism, and I still think we will eventually get something like it once the tech is really invisible, but the social aspect will take ages to sort out.
When they reach the age when all that is legal, the need for privacy goes down quite a bit.
You can spot the exact moment all the hype died, in that one post.
Google engineering was unwilling to remove such a useful feature... but Apple has withheld seemingly crucial features... so I still hope one day there'll be iGlasses.