For some values of 'idea'
Why not just have a phone/netbook combo that syncs wirelessly and shares a 3g connection. For extra points you could have some sort of remote view into the phone for people who really want to run phone apps on a larger screen. Of course, as pointed out upthread, that makes it pretty much a Foleo. But then the main problem with the Foleo was that it was overpriced and before its time.
Ultimately though, the problem's software not hardware. No amount of messing about with docking arrangements will solve the problem that people now have multiple devices with their data spread across them and no straightforward and non-proprietry method of syncing it all up.