It strikes me that as long as one is going to carry the pad part of it around, it might as well be a working pad without the phone docked into it.

I guess the only benefit is that when docked, the pad has the same data as the phone. But if that is the benefit, why not have a pad and a phone designed to sync together by cable or NFC?

Personally, if we want to go the docking phone/pad route, shrink the phone down to the size of an old Nokia 6210 or so and make it a basic phone that one can take out for a run, etc.

I see the need but my solution is a phablet - 6"+ screen that also works as a phone (Samsung Mega in my case).