Custom variables for visitors and actions?

It appears custom variables in 1.2 work well for adding data to visitor profiles. But is there a way for custom variables to be added to the action? I want to track additional details about the content that is viewed, i.e. the whether it’s a story or blog entry or photograph.

Not yet, but this might be added in a future release if demand is strong.

Is this the kind of thing I could achieve with a plug-in?

Yes