I have been using GTD for a couple of years and it works very well for me. To get focused on activities I use a combination of tools. Most of the tools are not bound to my computer because I found myself checking them all time. Instead, the tools are on my mobile devices because I can take a quick glance at them whenever I want.

I recommend the following tools:

Due for iPad, iPod touch or iPhone (needs iOS 4).

Pomodoro for Windows Phone 7. Here is a link to a description. The application is free and you can easily get it on the marketplace by typing “pomodoro”.