Tactor tries to guess the best action for current text selection. For example consider text containing http://xyz.com - an URL link. Or ~/Documents/MyPresentation.key - a presentation file. Both matchers and actions are fully customizable.
Tactor's idea is loosely based on Plan9's Plumber where any text can potentially be an action, although the actual technical implementation is very different. And it provides functionality somewhat similar to that of Apple Data Detectors in a way that is fully extensible and transparent.
UI scripting enabled