Hi Giorgio,
Mobile Kit Pro was released before we had the audio and video players. You'll need to add this to the style.comnfig in your copy of Mobile Kit skin:
<!--
<file cssvpath="/Data/style/jplayer/allskins.css" imagebasevpath="/Data/style/jplayer/">none</file>
<file cssvpath="/Data/style/jplayer/bluemonday/jplayer.blue.monday.css" imagebasevpath="/Data/style/jplayer/bluemonday/">none</file>
<file cssvpath="/Data/style/jplayer/pinkflag/jplayer.pink.flag.css" imagebasevpath="/Data/style/jplayer/pinkflag/">none</file>
-->
<file cssvpath="/Data/style/jplayer/bluemonday/jplayer.phone.css" imagebasevpath="/Data/style/jplayer/bluemonday/">none</file>
You may also want to upgrade to mojoPortal 2.3.8.1 because there was a fix in the video feature that affected some browsers.
Your mileage may vary when using the audio and video players on mobile, in my testing it works somewhat but there are some glitches. There may be problems on mobile if there is more than one jPlayer on the page so only use one instance on a page. Also only certain video format like .m4v work on IOS.
Hope that helps,
Joe