Here's the quick and dirty method that I'd use if I wanted a quick and dirty method. I'll pick "app launcher" because it'll work (I don't know how you'd go about power, and volume is a bit more of a pain).
button connected to arduino is read by max/msp. Upon reading proper signal, bangs a message to the [shell] object that says "open -a terminal" and the terminal opens.
hwaaaa...
Gabe