Now, cords wouldn't normally rate a mention...
... but, then, you can't usually upgrade your headphones without replacing the whole set.
Bose, the maker of the costly but delicious QuietComfort 2 and 3 noise cancelling headphones has released a set of cords that makes the 'phones iPhone compatible.
The $AU64.95 cords include an inline microphone so you can make and receive calls on your iPhone inbetween listening to high quality music, and simultaneously cancelling out the din of the city, bus or airplane around you.
The pricey but useful cord also comes with four tips to suit different
types of mobile phone headset socket other than the standard 3.5mm size.

Bose also quietly introduced a iPhone-compatible new version of its "on-ear" headphones which offer the Bose sound quality without the noise cancellation. The "Bose mobile on-ear headset" costs $AU299.00 and is available through Bose retailers, including Apple's Australian online store.