GREAT combination. H20 Audio sent me their new waterproof IPOD Shuffle casing to try out. It comes with a "swim belt" that is intended for a swimmer's body - it fits perfectly mounted on a Cabrinha waist harness.
The "pull cord" designed for the customer to unmount the IPOD doubles as a safety when the swimbelt is fed through the loop as shown in the picture.
I tried several headsets, and the one with the best sound quality comes from Aquapac. Aquapac makes a 100% waterproof set of ear buds that fit snugly, and thus provide wonderful sound quality... here are pictures of the combo mounted on a waist harness.