I’ve got no experience with using an iPhone as a swimming music player, but my first thought was that it’s simply too big and too heavy to attach to a swim goggle strap.
The wireless headphone feature of the new iPhone might have some possibilities. You could swim with waterproof wireless headphones (expensive) with your iPhone on the swim deck, but I’m not sure of the wireless range or if reception underwater is feasible. I‘d also be uncomfortable leaving an iPhone unattended.
The most highly rated MP3 swim player is the FINIS Duo Underwater MP3 player http://www.swimoutlet.com/p/finis-du...sion)-8139404/
. It’s on my “wish list”, but I just have a hard time justify buying one that I can only use while swimming.
Over the past couple of years, I’ve purchased several "waterproof MP3 players" from eBay. They’re shipped from China and they’re relatively cheap (less than US$20 for 8GB). I use them mostly for running and doing other exercises. Since they’re waterproof, my sweat won’t kill it. I’ve also used it in the sauna, Jacuzzi, and swimming pool.
There is a waterproof after-market Apple iPod Shuffle. It's expensive with a meager 2GB memory. Someone that I know bought one and it died after less than eight months.
The cheap eBay waterproof MP3 players come with waterproof earbuds, but they’re uncomfortable to wear and useless for competitive swimming since water pressure will push it out and off the ear. They might work if you swim with your head above the water.
There are waterproof swim earbuds designed for swimming. The best ones are those that come with a “custom” fit for your ear, but they’re expensive. There are several “Christmas tree” style earbuds that are cheaper and somewhat effective, but they have a short life expectancy (three to four months).
From my experience, the “Holy Grail” is finding a waterproof earbuds that’s suitable for competitive swim strokes that won’t bankrupt you and will last more than a few months. Water and pool chemicals are the enemy of electronics. If there’s a weakness in the waterproof seal, water will always find its way in to ruin it.
Listening to music while swimming has its benefits. I found myself swimming longer whenever I listened to music. When my waterproof earbuds died this summer, I dreaded doing those long swim laps.
I haven’t replaced my waterproof earbuds, but the MUSA Waterproof Earphone Headband http://www.swimoutlet.com/p/musa-wat...385/?color=207
looks interesting to me in that it has the “Christmas tree” style earbuds, a headband to keep it secure, and it’s not too expensive. If I decide to buy it, I’ll update this post.