The Sound ID is a Bluetooth headset
with its own iPhone app. EarPrint
is an app created just to control the sound of the headset -- you can tweak the audio in and out, change volume, and even find a lost headset directly from the iPhone itself. Not exactly revolutionary (personally, I've never really found a reason to use a Bluetooth headset -- when the actual iPhone didn't work for me, the wired headset works fine), but it's a nice bit of added functionality, especially if you know you'll always be using this headset with an iPhone.
The Sound ID is available for $130
(there are many cheaper BT headsets out there, but for the money it's a respectable piece of tech), and the EarPrint app is free.