I have successfully implemented calling GAE -> Azure Mobile Services -> Azure Notification HUB.
But I want to skip the Mobile Services step and call the notification HUB directly and I can't figure out how to send the authorization token. The returned error is:
Returned response: <Error><Code>401</Code><Detail>MissingAudience: The provided token does not 
specify the 'Audience'..TrackingId:6a9a452d-c3bf-4fed-b0b0-975210f7a13c_G14,TimeStamp:11/26/2013 12:47:40 PM</Detail></Error>
Here is my code:
    URL url = new URL("https://myapp-ns.servicebus.windows.net/myhubbie/messages/?api-version=2013-08");
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setConnectTimeout(60000);
    connection.setRequestMethod("POST");
    connection.setDoOutput(true);        
    connection.setRequestProperty("Content-Type", "application/json;charset=utf-8");
    connection.setRequestProperty("Authorization","WRAP access_token=\"mytoken_taken_from_azure_portal=\"");
    connection.setRequestProperty("ServiceBusNotification-Tags", tag);
    byte[] notificationMessage = new byte[0];
    try 
    {
        notificationMessage = json.getBytes("UTF-8");
    } 
    catch (UnsupportedEncodingException e) 
    {           
        e.printStackTrace();
        log.warning("Error encoding toast message to UTF8! Error=" + e.getMessage());
    }
    connection.setRequestProperty("Content-Length", String.valueOf(notificationMessage.length));        
    OutputStream ostream = connection.getOutputStream();        
    ostream.write(notificationMessage);
    ostream.flush();
    ostream.close();
    int responseCode = connection.getResponseCode();