Is a "reverse" supercharger possible? Does it exist?

Let me explain.

A normal supercharger uses power from the engine to compress the air for the intake, effectively increasing engine displacement. A turbo uses a turbine to draw power from the hot exhaust gasses to power the compressor. In theory, this doesn't "steal" any power from the engine like a supercharger does.

But what if you hooked the exhaust turbine from a turbocharger directly to the driveshaft? Instead of stealing engine power to compress intake gas, like a supercharger does, it would extract energy from the hot exhaust gasses and send that power directly to the drivetrain, effectively salvaging waste heat from the exhaust to increase power and fuel efficiency. In other words, this is a turbocharger that powers the driveshaft, not a compressor.

I've heard that some trucks already use this system, but searches turned up nothing. Does anyone know if this exists, or if it is even plausible?