Consider a LCD that sits directly on the serial port. Then, messages are only a a Serial.print command away. With Arduino 1.0, the serial port is no longer blocking the CPU the way it used to. See Mark Sprouls shield description for what I mean. A similar shield can be bought at Unified Microsystems for $35. But I would prefer Marks shield because it's open source... see if he can sell you a PCB and you then populate it with the components of your choice.
I can't tell what pins the SainShield uses... it's not in the shieldslist either. HTH