connecting two CPUs together efficiently is hard, and not something that you are going to do with a docking station (the connector alone will be a large percentage of the size of the mobile device, you aren't just talking about a USB cable or something like that.
Also, a docking station with it's own CPU, memory, etc isn't cheap, but it also already exists (it's called a "desktop computer")
what you seem to be wanting is checkpoint/restore capability to move running applications from one server to another. with the appropriate emulation, the desktop doesn't need to have the same processor architecture that the mobile device has
docking stations are much simpler, they are little more than convienient ways to plug in several devices at once instead of having multiple wires.