Here is a pair of glasses that uses sensors to measure your brain activity and darken when you are not focused. The Narbis uses Bluetooth to connect to your smartphone. It comes with various programs to improve your focus, sleep, mood, and performance. By practicing to keep your glasses clear, you train your brain to focus better.
With the Narbis, you can train when you are reading a book, working, or even watching TV. Training should be 30-45 minutes according to the developers. You can find this wearable device on Kickstarter.