Webtrate is available for Windows and Mac OS X and costs $8 to download. It's a solid application with a clean interface, and it does exactly what it sets out to do. That said, it has some shortcomings. For one thing, it lacks a timer, so there's no way to see how long you have until you're back online. On the one hand, this lends a Zen-like feel to the app — there's no way to see the time, so you may as well not think about it. On the other hand, it's annoying and problematic for people who work on deadlines or in collaboration.
Webtrate is also not for everyone. If you're trying to finish a creative project, such as a script, book, or long-form article, Webtrate can help you stay focused and minimize all distractions. But if you're a freelance writer or a telecommuter, it's probably impossible for you to work completely Internet-less for long periods of time. Webtrate is an all-or-nothing deal and that limits its appeal.
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