According to a filing with the EU patent office, Ferrari is developing a forced-induction engine that contains a turbine in the interior of the exhaust duct that powers an electric generator that stores energy. The electrical energy is then directed to an electric motor that powers the front wheels, and it also sends power to an electrically assisted compressor that can send air into the engine itself.
There are a couple advantages to this design, as Autoguide notes.
First and foremost, there is the potential to reduce turbo lag because the electric motor powering the front wheels can compensate by providing a boost of power when needed.
Second, Ferrari expects this turbine to improve exhaust sound: the faster the turbine spins, the more high-pitched the exhaust tone becomes, while slower spin generates a deeper tone. The adjustable turbine will be able to modulate the exhaust note as required, as opposed to an exhaust valve which really has just two settings. This doesn't mean the setting of this turbine will govern the engine's performance -- that's where the electrical generator comes in, providing power even if the turbine is modulated to turn slower. At least that's the goal of the design.