I use Motorola S10 headset. Works like a charm for me. To make it work,you just have  to pair your headset with the iphone. 

Steps:

1)Enable Bluetooth on your Iphone.(Settings>General>Bluetooth)

2)Pair your headset with Iphone as per the instruction manual. Normally, you just have to turn on the headset and iphone will automatically detect the bluetooth.

http://www.amazon.com/Motorola-S10-HD-Bluetooth-Headphones-Packaging/dp/B004BHCSQC/ref=sr_1_1?ie=UTF8&qid=1322916415&sr=8-1

Hope this helps.