Firefox Time Tracker : update 2 February 2015
For now it's very basic. You will see this icon next to the close button:
Yes I know I should create a custom icon :D but I was too busy coding. You will then see some basic statistics of the day.
I'm now working on making this page nice with pretty graphics and more statistics (week, month, tracking of the most visited website of the week...).
So if you want to try my plugin, know that it works (so far)! And that you should pay this blog a visit because I'm planning on updating it.