Check out Arm Pocket's Sport20. It's gotten good review from the running community. Want to buy one myself. http://www.armpocket.com/index.php?page=p_sport-new2.php&id=2
The dualfit looks better. I don't think I want a small backpack on my arm. Won't need to pack anything.
If anyone uses Nike+ with their iPhone 3GS or 4 I started a thread in Tips & Tricks and am trying to get more info on using the headphones controls.
Thanks.