Lars,
Don't know of any web based or DNN modules. I've used a windows form app to do it, and I suppose it's possible, just not something I've done. I was wondering if you could describe the need for it, and what features you envision. I may give something like that a shot, as I do have some situations that it would make a module like that particularly useful.
At present, I use VS.Net, or text editor, but my data sources are not very large. Give me a wish list, and I'll see about modifying my windows form app.
Not a bad idea...