I am not aware of any free SMF mods out there that do this (though that doesn't mean there aren't any). I do know that there are quite a few web-based services that offer what you want, though of course they charge varying monthly fees. For instance, the tools available from this
site offer an API that could be used to give the kind of functionality you want.
I imagine you're wanting something simple to use and, if possible, free. I have a friend who might know something. I'll email him. If I learn anything of further use, I'll report back.