I made a macOS app [1] after reading this book that helps keep track of deep focus sessions.
[1] (free) https://itunes.apple.com/us/app/zen-time/id1089216789?mt=12
12 karma · joined March 22, 2015
[1] (free) https://itunes.apple.com/us/app/zen-time/id1089216789?mt=12