How to Use Bluetooth on Your iPhone
On the iPhone, you can use a short-range wireless technology named Bluetooth to communicate with a compatible Bluetooth headset or hands-free car kit. These optional iPhone headsets and kits are made by Apple and many others. They've become more of a big deal as a number of states and municipalities around the United States make it illegal to hold a phone to your mouth and ear to gab while you're driving.
To ensure that the iPhone works with one of these devices, it has to be wirelessly paired, or coupled, with the chosen device:
Apple's headset: With the optional iPhone Bluetooth headset that Apple sells, you can automatically pair the devices by placing the iPhone and headset in a dual dock (supplied with the headset), which you connect to your computer.
Third-party accessories: If you're using a third-party accessory, follow the instructions that came with that headset or car kit so that it becomes discoverable, or ready to be paired with your iPhone. Then turn on Bluetooth (under General on the Settings screen) so that the iPhone can find such nearby devices and the device can find the iPhone.
Bluetooth works up to a range of about 30 feet.
You know Bluetooth is turned on when you see the Bluetooth icon on the status bar. If the symbol is blue or white, the iPhone is communicating wirelessly with a connected device. (The color differences provide contrast to whatever is behind the icon.) If it's gray, Bluetooth is turned on in the iPhone, but a paired device isn't nearby or isn't turned on.
You can unpair a device:
On the iPhone Home screen, tap Settings→General→Bluetooth.
Tap the device you want to unpair from the device list that appears on the Bluetooth Settings screen.
The word Connected becomes Not Connected.
Tap the device again to reconnect.
You can even divorce a Bluetooth device from the iPhone:
On the Bluetooth Settings screen, tap the right arrow in the blue circle to the right of the Bluetooth device you're unceremoniously dumping.
On the screen that appears, tap Forget This Device.
At least you won't have to pay alimony.
iOS 3 and 4 provide support for stereo Bluetooth headphones, car kits, and other accessories, so you can stream stereo audio from the iPhone to those devices. Sadly, stereo Bluetooth still doesn't work on the original iPhone.
The iPhone can tap into Bluetooth through peer-to-peer connectivity. Engage in multiplayer games with other nearby iPhone users. You can also do such things as exchange business cards, share pictures, and send short notes. And you don't even have to pair the devices, like you do with a headset or car kit.
You still can't use Bluetooth to exchange files or sync between an iPhone and a computer. Nor can you use it to print stuff from the iPhone on a Bluetooth printer. That's because the iPhone doesn't support any Bluetooth profiles (or specifications) required to allow such wireless stunts to take place.