GNOME Shell extension providing a countdown timer in the top panel

 Installing this package adds a timer application to the GNOME Shell top panel.
 With it you can start a timer of any duration and when elapsed, you'll get a
 notification. You can also preconfigure various durations to avoid having
 to retype them.
 .
 It's a natural replacement of the "timer applet" for GNOME 2 (or 3 in
 fallback mode).
 .
 Users of the Pomodoro method will find this extension very useful.