Could you use the Casimir effect to send messages across arbitrarily-large distances with carefully-tuned Casimir plates? 

Obviously, relativity would preclude FTL information transfer, *but* as long as one did not try to *measure* any signal delay (i.e. impose an external reference frame of time), it would, in *theory*, be communicated instantaneously (presumably along an extra-dimensional Calibi-Yau surface/"brane").