Just in case a Nokia marketing guy passes by, here is what I would love as a companion phone for my N800:
- GSM/GPRS/3G compliant
- Bluetooth
- Basic SIM / phone / SMS functions so the phone is usable stand alone.
- A HUGE battery life
- basic screen (even black & white)
- As small as possible
- Uses the same charger as the N800! It can even be sold without
- All functions accessible through the N800: making / receiving calls and SMS, managing contacts (sync with N800 contact list), and other configuration (i.e. network selection / configuration).

No camera, no music, no video, no games, no calendar, no PIM, no nothing. I have the N800 for that purpose.

More or less a 8310 with BT and 3G.

I would also consider a more expensive model that would integrate a GPS receiver (bundled with Navicore )

What would be yours?