Is there a pomodoro app that's available for Ubuntu 12.04 that can be installed using sudo or from the package manager?
For Gnome-shell. You can use this extension in GNOME shell for pomodoro indicator. It works out of the box in many distros, like Ubuntu 17.10 (which doesn't come with Unity anymore).
Old versions were installed through:
Current version that works on my Ubuntu 20 is install-able through apt:
sudo apt-get install gnome-shell-pomodoro
Homepage with instructions for installing on different OS distributions and versions: http://gnomepomodoro.org/
For Unity. The pomodoro-indicator as referenced by the other answerer doesn't work straight out of the box. We first have to fix the icon so it appears on the Unity panel.
Follow the commands and hopefully it works for you:
wget https://launchpad.net/pomodoro-indicator/trunk/0.0.2/+download/pomodoro-indicator-0.0.2.tar.gz
wget https://launchpad.net/pomodoro-indicator/trunk/0.0.1/+download/pomodoro-indicator-0.0.1.tar.gz
tar xvf pomodoro-indicator-0.0.2.tar.gz
tar xvf pomodoro-indicator-0.0.1.tar.gz
cp -R pomodoro-indicator-0.0.2/* pomodoro-indicator-0.0.1/
cd pomodoro-indicator-0.0.1; gedit setup.py
In line 112, remove # from the following line:
#package_data = {"pomodoro": ["images/*.png", ]}
Save the file.
sudo python setup.py install
pomodoro-indicator
Pomodoro indicator will now appear in the Unity panel.
