190
Your Brain Waves Are Up for Sale. A New Law Wants to Change That.
(www.nytimes.com)
This is a most excellent place for technology news and articles.
At an absolute minimum 20. We aren't seeing any useful systems that work on any scale at all yet. The iphone made smart phones pseudo mandatory but they were preceded by decades of development with several generations of usable devices. If I had to guess it's probably closer to 30 years if tech decides to go in that direction which itself isn't guaranteed.