To be clear, this is easiest to use with something like a BUTTON since there's no need for obtaining info. I was going to try to make this more complex :-) but it isn't really needed. If you have, say, a slider you'd just use the same approach. In the state which responds to the event, just use the Get Property action, drag the slider GO from the Hierarchy panel into the Target Object param/box in the Stare inspector, and select the property "Value". This will get you the slider's value as a float from 0 to 1.
There is a need to programmatically set up certain EZGUI controls but that's best handled thru scripting rather than actions. I may create some actions for these as the need requires.