I'd like to build a Drupal 7 module that generates a block which contains (along with some static HTML to be used as template for a JavaScript library) a node-specific value to be passed on to a web service. (The web service will return relevant data for the contents of the node.)
How should a block receive node-specific data? Module configuration seems to be global, and blocks cannot be configured individually.
Should I modify the main content-type of the node by adding this "node-specific data" as an extra field even if this value is only used in my module?