I couldn't find anything like it, which surprises me. It should be in the interest of companies selling screenreaders that the web is accessible with them. Creating a service where you can submit a link and it shows you a textual representation of how the screenreader sees the page would be immensely useful.
These scans are in my experience always just that: they read the source and match it against a set of common anti-patterns. I was talking about something that would tell me how common commercial screen readers interpret an arbitrary new construct. If you have a specific reference to something else, please send me a link!
Screen readers often cost significant amounts of money, and are not trivial to "just turn on".
