The ones on new cars are only actuated when the vehicle is placed in park, so it's actually a parking brake. The Wilwood brake would be able to be applied by a switch, and it's all or none. If you tried to use it as an emergency brake, it would lock the rear tires up immediately when you applied the switch. We had them on service bucket trucks at work, and when applied...the truck was locked down and you couldn't budge it! They were made by a company called Mico Brake, and there used to be both hydraulic and electric versions. The latest ones we had were electric. I'm pretty sure jcc meant that it should not be used for a brake in an emergency....like if your regular brakes went out, but only used as a parking brake. 2 totally different things.