cool idea, i'm not sure if the guts of the phone would be able to be housed in the keyboard section though because bluetooth is still not quite reliable enough to send a continuous video signal over.
you could theoretically do something similar to this with one of the imate models or just about any other PDA really... if you were to take something like a Dell Axim with bluetooth and pair it to a bluetooth enabled cellphone and bluetooth keyboard, you could basically do the same thing. granted this solution wouldn't really be as cool or "portable" as your idea.
