Contact Form 7 API plugin
Yes, we did with the Contact Form 7 API (which we created for a specific customer as you mentioned :-))

The Contact Form 7 API submits the form data with an API WpCivi Submit with a form type which links to the class that is called in CiviCRM. You can find the CiviCRM part of the customer extension we created here, hope that helps you on your way!