It's a very simple app hosted on Google App Engine. At this point I don't think I have the locations quite right but it's pretty close.
You can either put the grid locator in the path or if not a form is shown.
Please give it a try, perhaps look up some of the WSPR spots, and let me know if it's broken. It would be great is wsprnet.org had links on the Grid items to something like this.