Reading with monitor for a long time is unavoidable to people and it strains your eyes.
It's necessary to rest your eyes every 50 minutes you spent with monitor.
And this extension notices you on a timely basis w/ a decent user interface.
Why this extension require Access your data for all websites?
Since you are able to set your own notification sound, which may located on any server. I thought asking this permission is required. I will minimize this once I knew there is better solution. You may concerned about security. I can guarantee that the program is build directly from source, and the source code is on GitHub, I didn't abuse with this permission.