I keep my phone in my pocket while working out... I wear long basketball shorts so it's not comming out of my pocket... The largest card it's supposed to handle is a 32gb. But then again... I haven't seen any bigger ones.
I use wired and bluetooth headphones while working out and in my wife's car I hook up with a cassette deck adapter as well. In my car... I use an fm tramsmitter designed for an ipod... I hook up an insignia bluetooth receiver to the ipod connector and my phone sends the music via bluetooth to it.
so... This...
plugs into this...
And it sends the music to my stereo.