there is no added sensor for the ebrake they just tap into the the factory one. installing a remote start on a MTX vs ATX is usually just 2 wires. one goes to the clutch other to the ebrake. ATX these are just grounded or not used depending on the remote starter.
Viney266 gave you how the user activates the remote start. if a door is opened, truck, hood, ebrake looses continuity, or applied brakes will cause no start if it happens when it applies power to ACC. an other sensor can also be wired in to de activate the remote start.