Some interesting info taken from one of the Ferrari sites....
Magnetic Brake Systems
Radical changes to brakes will happen in forthcoming model years that will revolutionize them making them ruthlessly efficient and drastically reducing their weight, parts and complexity. There is no question that electronic brakes will happen, their benefits are clear, it is more about ‘when’ rather than ‘if’. Already new magnetic brakes exist and work on prototype vehicles. They stop faster [no latency from fluids] and require no serviceable parts and actually recover energy to be later used for acceleration again rather than waste the energy as heat. At the moment they are currently illegal to use on a public road because there are no government agreement’s in place for true ‘brake by wire’ systems.
So what is good about Magnetic brakes? Well firstly there will be no brake discs to wear out, no brake fade ever, no pads to replace, no corrosive fluid to change, no brake servicing required at all and weigh next to nothing. They don't need a master servo, no fluids, no brake lines to corrode, no nothing, they fit inside the wheel and require one tenth of the energy of mechanical brakes. They will last the lifetime of the vehicle and actually contribute to save energy rather than waste it. They sound amazing don’t they and they are. Perhaps a little TOO good. No parts to replace or things to go wrong! These brakes are so simple and so obvious, one wonders why they where not introduced years ago. Perhaps the interests and jobs of companies and people in the braking industry have had something to say about their slow uptake. There are companies now working on alternatives which have bearings in so at least there are some things that need replacing.
How do they work?
Firstly consider 'conventional' analogue brakes, they basically work by converting rotational energy of the wheel spinning into heat via means of friction [from pads coming into contact with steel or carbon ceramic discs]. This happens when force from the brake pedal squashes [hydraulic] brake fluid which pushes the pad against the disc and the friction takes place converting the wheels rotational energy into heat which is dissipated away as waste energy.
Next generation magnetic brakes don’t waste energy, they generate electric power from the rotational energy [just like an electric generator does] and use the recovered energy to power electo-magnets which do the bit in slowing you down. Not only does this save the waste of the energy used to accelerate in the first place [not all of the energy is needed for braking which can be stored] it allows non friction braking which means nothing wears out. The best possible braking up to the maximum level of maximum traction for any road surface when hooked into systems which measure brake slip. You always get the best possible braking for all road surfaces.