First tep would be to look for some ICs designed to measure voltage. or find an old digital multimeter and hack it. I'm all about the hardware hacks.
Ok yeah. I kind of have the idea already....
I'm taking the input of a piezo (measures velocity, 'how hard' it's been touched/hit) so that is in voltage
Take that line of voltage, sample with an A->D chip. Then that value needs to be pumped into the rs232 line by the PIC with some event messages, like start of text, end of text, the command, the value
Again what makes this easy is its a one shot.
I got all these other extended features I want too, but I gotta get this at least work first