WOT+activation switch

I wondwer if anybody used WOT switch + a manual activation button? Lets say I'm runing autocross or road race, during some parts of the track I would like to hit N2O. I don't wont N2O to spray evry time I floor my gas pedal,but I don't wont to sray if my throttel is not wide open. So I was thinking about using WOT switch as a precaution unit and the actual spraing activated by a button(probably located on a stick-shift)
That way I can get into my car, started up, arm N2O, go race and punch it here and there. Did anybody used such setup?:

a friend of mine used that exact set up when we installed nos into his Saturn last year. Worked like a charm.