This is a great extension on its own and I recommend it. I also use the iphone app (which has a small pricetag but is totally worth it). Would give it five stars if the two could be synced with regard to total time focused (although allowing for separate coin collection/trees to grow on each device is good, I'd sacrifice that for a more accurate count of actual time focused).

Another feature would, by itself, also push this to five stars: allowing one to set a countdown to a tree being planted - that would be super helpful for us break-extenders!