Nice idea! I was thinking of doing the same. Where did you mount the button? I was thinking of putting it where the traction control button would be, if I had it.
One question for ya though: Is it just a small current going through the key ignition switch for a relay that actually powers the starter motor, or is it the full current running through it for the starter? If its just a small current for the relay, then I'm sure I could use just about any button.