I'm going to start on connecting my calculator to my phone soon, I've posted to the arduino forum to see if I can find a compact enough bluetooth-enabled board. From there I'm going to use the ArTICL library and connect the arduino to my calculator and my phone. My primary focus is programming apps so this shouldn't be too difficult. Once I've got this all working I'm going to see if I can find a way to wire the arduino to the calculator internally, without using the I/O port. This is probably going to be the most difficult part as I'm not too experienced in this area.

Any tips, suggestions, or thoughts?