Is there a Pomodoro app available?

Tomate

RELEASE=`sed -n 's/VERSION_ID="\(.*\)"/\1/p' /etc/os-release`
sudo wget -O- http://download.opensuse.org/repositories/home:/eliostvs:/tomate/xUbuntu_$RELEASE/Release.key | sudo apt-key add -
sudo bash -c "echo 'deb http://download.opensuse.org/repositories/home:/eliostvs:/tomate/xUbuntu_$RELEASE/ ./' > /etc/apt/sources.list.d/tomate.list"
sudo apt-get update && sudo apt-get install tomate-gtk

gnome-shell-pomodoro

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).

• https://extensions.gnome.org/extension/53/pomodoro/

Homepage with instructions for installing on Ubuntu: http://gnomepomodoro.org/

malev's pomodoro-indicator

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.

Reference

• https://answers.launchpad.net/pomodoro-indicator/+question/198506

Atareao's pomodoro-indicator

Having tried others, I recommend Atareao's Pomodoro Indicator App.

Why? It is simple, beautiful, configurable, has been tested in ubuntu 14.04, 14.10, 15.04, 16.04. It has a PPA and the developer is known for writing quality indicator apps such as my-weather-indicator.

My favourite thing is that the icon changes to reflect how much time is left. Here's a time-lapse screen capture I made:

This is what the preferences look like (polar night gtk theme):

Installation: Copy and paste the following in the terminal:

sudo add-apt-repository ppa:atareao/atareao
sudo apt-get update
sudo apt-get install pomodoro-indicator