Ok, how about using the message event to receive data from the app? Not only return values, imagine an app updating the browser as data changes like:

    <a href="wallst.com?ticker=AAPL" action="stocks" onmessage="update(event)">

Kind of server events attached to the message event of an actionable link. Everything scriptable.

You know, just throwing ideas to the wall to see if something sticks.