Apparatus is a NodeBox-like interactive diagram editor from Alan Kay's CDG think tank:
I post this link here because it shows an interesting approach to enabling user input directly to diagrams. NodeBox currently does static visualizations and animations but, despite it's richly interactive design environment, cannot yet create end user interactives. I know the team is thinking about adding this capability. I don't know if the Apparatus approach would work for NodeBox, but I think it's worthy of study.
Thoughts?
John