Productivity Challenge Timer is described as 'Pomodoro timer which aims to help you be more productive, more focused, waste less time and so on, you already know all that stuff' and is a Pomodoro Timer in the Office & Productivity category. There are more than 10 alternatives to Productivity Challenge Timer for a variety of platforms, including Online / Web-based, iPhone, iPad, Android and Mac. The best alternative is Gnome Pomodoro, which is both free and Open Source. Other great apps like Productivity Challenge Timer are Pomofocus (Free), TomatoBar (Free, Open Source), PomoPlanner.app (Free) and Timmy - Social Pomodoro Timer (Free).
PomoPlanner.app is a pomodoro-based daily planner webapp that allows you to plan and track your main daily tasks, mini-tasks, physical exercise but also to take notes on things you're grateful about, things you've learned and more!.
Studyzone is a shareable and completely customizable pomodoro timer for teams and study groups. You can study alone or share a room with others. Studyzone is meant for students, developers, teams or just people that need some extra focus.
Timist combines the unique Timist Session System with time tracking. You can create different timers and track the time for each of them. It also lets you break your time down into concrete intervals, separated by short breaks.