There's a very cool video at Ralf Ackermann's blog showing an iPhone receiving input from an Apple Bluetooth keyboard. Of course, it requires a jailbroken phone, but Ralf claims that it works in all iPhone apps that make use of the keyboard.
This reminds me of the Stowaway Keyboard I used with my old Palm IIIe. I didn't mind Graffiti as much as some others did, but attaching that keyboard to my Palm increased its usefulness many times over.
Of course, I'd love to use a wireless keyboard with my iPhone. Since I won't be jailbreaking, here's hoping Apple (or someone else) will make this available to scaredy cats like me.