Agree with Waynne, except about the spinning turbo. The turbo will stop spinning pretty quickly once engine is switched off. The exhaust impeller is connected to the intake one. Pressure quickly builds up in the intake track once engine is switched off, stopping both impellers.
The turbo will be cherry red after a hard run and, as the oil pipes supplying the turbo are small, the oil will quiickly burn and clog up the pipes if engine is switched off with turbo glowing. Not good.
Instead of spending your hard-earned money on what is, basically, a gimmick, simply ease off the throttle a little way from your destination
If you can't do this, then simply let the engine idle for a few minutes before switching it off (this is all the turbo timer does).
However, one advantage of the timer is that you can lock your car up whilst engine is running.