Module Dev: How to attach a button to a field? I would like to build a module whereby a user can enable a button per field, and when the user clicks on it, it gets the field contents and posts it to a service.

If there are any modules like this that would be great as well as an example.
This example comes close: Publishing to Facebook Wall. It shows how to post a facebook message when a node or comment form is submitted, and provide an option to opt-out on the node or comment form.