The Prius is first and foremost a SULEV vehicle, designed to minimize emissions. Minimizing fuel consumption is the second most important consideration. To achieve SULEV, heating of the catalytic converter, and various other bits and pieces including the O2 sensor, needs to occur as fast as possible. Accordingly, mileage is usually quite low for the first few minutes to heat rapidly. In addtion, the Prius has an electric heater to supplement cabin heating in cold climates, until the engine is warm enough. I'm not sure if other hybrids have this.

The bottom line is that I don't think there is a need for a friction heating device for the Prius. With the engine running more than usual for the first few minutes, the equivalent effects is created by charging the battery. Some people have suggested running the Prius in EV mode as much as possible just before shutdown, at the end of trips. That way, some of the energy 'burned' during warm up is used to charge the battery.