There are a couple of usability testing tools that match our preferred ‘guerrilla’ approach. Eye-tracking has long been a useful technique when designing compelling user interfaces, however the equipment and software associated with it is expensive and typically requires the use of specialist firms. Crazy Egg is a cheaper, software-only solution that produces heat maps based on mouse movement. This movement has a strong correlation with gaze, and can be used as a reasonable approximation. Silverback captures not only the screen during a test, but also records the face and voice of the user. This can be invaluable in sharing rich test experiences with the wider development team.