In a typical pairing of a cell phone and a bluetooth device, the “smart” phone drives the “dumb” bluetooth. The computational brains and user interface controls live inside the cell phone together with the antenna. The bluetooth device simply follows orders. For example, a bluetooth headset acts as an alternate microphone and speaker for the phone. The bluetooth truly is an accessory to the phone.

I’d like a reverse sort of bluetooth device. A bluetooth “sethead”, if you will. The cellular antenna lives inside the earpiece, or maybe stays inside your pocket or bag — technically this is the “phone” but it is a dumb device with no screen or interface. The “bluetooth” part is the thing you hold in your hand with all the smarts: the processor, the address book, the screen, the controls, the camera, the gps, another microphone and speaker — everything you normally expect in a phone except the antenna.

Why do I want this? If it existed, I could choose any carrier with any phone. I select a dumb phone from the best carrier and a smart sethead from the best hardware company. A version of an iPod touch with a camera, microphone, and gps would make an ideal sethead.

A MiFi device comes close: it’s a dumb cellular antenna that creates as a mobile wifi hotspot that can connect you to Skype, etc. (I have one from Verizon Wireless and love it.) But it’s not “always on”. MiFi + iPod is great for making calls but not for receiving calls, so is not sufficient for replacing a cell phone.

Sure, the advent of setheads would speed the carriers’ transformation into “dumb pipes”, something they are resisting, but that is inevitable anyway.