Clive it not just the calipers.
It requires a full abs system.
It is constantly live and if it sees the car move as the system cools it clamps up to hold it.
I think a design requirement also requires the horn , hazards and h/lamps must all go off if it becomes a run away to let you know you need to get the f**k out of the way.
You also need a scanner to fit brake pads as you need to retract the pistons.
Lot of work for a handbrake.
Jim