Background: This is a request for something that may not exist yet, but I've been meaning to build one for a long time. First I will ask if anyone has seen anything like it yet.

Suppose you have an arbitrary JSON structure like the following:

{
    'str_title':'My Employee List'
    ,'str_lastmod': '2009-June-15'
    ,'arr_list':[
        {'firstname':'john','lastname':'doe','age':'33',}
        ,{'firstname':'jane','lastname':'doe','age':'34',}
        ,{'firstname':'samuel','lastname':'doe','age':'35',}
    ]
}

Question: Is there a web-based JSON editor that could take a structure like this, and automatically allow the user to modify this in a user-friendly GUI?

Example: Imagine an auto-generated HTML form that displays 2 input-type-text controls for both title and lastmod, and a table of input-type-text controls with three columns and three rows for arr_list ... with the ability to delete or add additional rows by clicking on a [+][X] next to each row in the table.

Big Idea: The "big idea" behind this is that the user would be able to specify any arbitrary (non-recursive) JSON structure and then also be able to edit the structure with a GUI-based interaction (this would be similar to the "XML Editor Grid View" in XML Spy).