It really is more of a gimmicky thing than a practical thought. My plan is to have the driver insert the key and turn, then press the button. Which is the method in a few cars I've been in, as you usually have to uslock the steering anyway.
My only hiccup at the minute is do I just give it the ability to start the engine and stop the engine, or just the former? As I could see myself leaning on the button, as I usually rest my arm there. Really depends on the button I guess.
Does any one have any idea of the wiring that it would require?