I think phonegap is your only chance, because you can't use your mobile features like audio recording in your browser.
Im also attempting to ue the phone gap audio recorder plugin, however it seems to be slightly glitchy. Also once the recoding is made i cant find a way to replay audio in mendix native app. The video audio players all seem to need a youtube or vimeo URL, i am trying to save the recording in a .fileDocument object annd play back from the DB.
I would expect the Phonegap Media object is what you need.
I would be interested to hear about your experiences. I'm finishing up on mobile widgets for camera and geoposition. I use these in combination with phonegap / cordova.
HTML 5 has defined Media Capture and some mobile browser have implemented parts. See this. This is experimental and not yet fully standardized.