The settings area has some default sites added but you can add more to customize to your needs
Forest does a nice job of putting a popup up when you go to one of those sites saying "Your tree is still growing!" and asks if you want to give up, so you don't inadvertently kill your tree with a habitual news site check.
There's a $2 app you can sync with to track your progress in the longer term and actually build forests but if all you want to do is build trees with no record of all your progress, it's great for that.
A desktop app that has a free time tracking capability
Can act as an automated research and dissertation log
Form an Accountability Writing Group - This document was created for the graduate student audience at the University of Notre Dame. While it has programming specific to this student population, there are guidelines that can help anyone who seeks to find support for more productive writing in a group of two or more.