Pairing an iPhone 4 with an Apple bluetooth keyboard

For the past two years I've been looking forward to using an external keyboard with my iPhone, much as we used to use an external kb with our Palm devices. I now have an iPhone 4, so I tried pairing it with my 27" iMac keyboard (already paired with the iMac).

I followed this user guide procedure, but it didn't work at first:

1. In Settings, choose General > Bluetooth.

2. If Bluetooth isn’t already turned on, tap the Bluetooth switch.

3. Press the power button on the Apple Wireless Keyboard to turn it on.

4. On iPhone, tap the entry for the keyboard under Devices.

Once the keyboard is paired with iPhone, it connects whenever the keyboard is within range (up to 30 feet). You can tell the keyboard is connected if the onscreen keyboard doesn’t appear when you tap in a text field.

The iPhone Bluetooth settings simply showed the spinning "wheel" next to "Devices" and the phrase "Now discoverable". I think the problem was that the keyboard was already paired to my iMac. My Bluetooth peripheral experience is limited, but this seems a sensible if inevitably confusing behavior.

It took a while to get things to work. At one point the iPhone said it found a "Wireless Keyboard" but not an "Apple Wireless Keyboard". I did the following (not all necessary I'm sure):

1. Went very far away from my iMac and down a flight of stairs. In my house Bluetooth really reaches.
2. Removed batteries from kb and reinserted.
3. Followed above procedures but pressed and held the power button until it went off.
4. Pressed the power button on the kb until it started blinking.

Then the iPhone found the keyboard. I tapped the entry and was asked to enter a code on the keyboard.

They then paired.

Once the two are paired the iPhone's keyboard no longer appears when the kb is in range. I turned off Bluetooth to get it back.

To repair the kb to my iMac I again held the power button until it powered down. Then I held it until it restarted and began blinking. It then reconnected.

This was trickier than I'd expected, but now I know it works. I'll be looking for an iPhone specific bluetooth keyboard that includes a cradle to hold the iphone, an iPhone-touch-screen compatible stylus to facilitate interaction with a mounted device, a form fact that is more compact than Apple's kb, and an optional charger.

Update: A bit more on unpairing from Apple's excellent iPhone iOS4 user guide (it's on my Reader.app bookshelf in my iPhone and it's a default shortcut in Safari on new installs):

Once the keyboard is paired with iPhone, it connects whenever the keyboard is within range (up to 30 feet). You can tell the keyboard is connected if the onscreen keyboard doesn’t appear when you tap in a text field.

Switch the language when using a hardware keyboard: Press and hold the Command key, then tap the space bar to display a list of available languages. Tap the space bar again to choose a different language.

Disconnect a wireless keyboard from iPhone: Press and hold the power button on the keyboard until the green light goes off.

iPhone disconnects the keyboard when it’s out of range.

Unpair a wireless keyboard from iPhone: In Settings, choose General > Bluetooth and tap the entry for the keyboard under Devices, then tap “Forget this Device.”