Nothing but the best for Casso - I've got the
H2O Amphibx waterproof case for my iPhone and the
H2O Surge - Laird Hamilton Signature waterproof headphones. Awesome quality stuff. Highly recommended.
An arm band comes with the case and I've also got an extra waist band. Great for listening to tunes while flatwater paddling and even good in the surf on lonely days (doesn't happen very often in Sydney).
Plus, in an emergency, you've always got your phone with you. You have to take it out of the case to talk into it (no mic in headset) but you can SMS via the iPhone touch screen though the clear window.
It's not cheap (RRP: AUD$250 - I think) but worth it if you do lots of solo flatwater paddling and like listening to tunes while you paddle.
Oh and before you ask for your $10 GoPro donations back because you think I can afford all the gadgets - I won my setup in a SUP photo contest on StandUpZone.com.