WHAT IS THE BEST HOLDER/ CARRIER FOR MY IPHONE WHILE RUNNING 12 MILES OR BIKING LONG DISTANCE?

What is the most appropriate holder/ conduit for my iPhone 3GS whilst using twelve miles or biking prolonged distance? Something shock proof, or H2O resistant but can be carried easily. The Armband things seems so bulky, does any one have any ideas?
Thanks in advance.