The TYPO3 extension Seminars uses Formidable for rendering forms and some Java-Script wigdets. We're using jQuery for all our JS based scripting and jQuery UI for a few User Interface related purposes. To achieve a consistent look for all JS UIs we wanted to change the pretty unusable and unsexy looking default DHTML Calendar of formidable with the jQuery UI one.
To change the hardcoded formidable rendering I've implemented an own renderlet based upon the example renderlet extension by Jerome Schneider.
I released my resulting extension to the TER as I was asked so in the Mailinglist. Please give feedback or ask a question via email or (better) as a comment down below.