Pomodoro timer with tracking, reporting and other powerful sets of features. You can add a chrome extension for web and directly enable Pomodoro mode from the Toggl extension. Available on iOS/Android/Mac/Windows, everywhere.
Allows you to easily add any sites you'd like to block during your focused period -- 5-minute cooldown also built in.
The only way to disable to the lockout is to uninstall the extension completely. So far so good!