I used a bluetooth adapter with my Nano at the gym it really sucked the power from the ipod. I charged the headphones everyday after a 2 hour workout just so It wouldn't go dead on me while I was working out. Below is pics of the Sony Ericsson's bluetooth headphones I mentioned in an earlier post they are very compact. The other pic are of the Sony SONY MDR-AS50G that I currently use they seem to hold up well at the gym but they are wired.
Link for the Sony Ericsson's
http://www.sonyericsson.com/cws/prod...?cc=gb&lc=en#a