They probably are completely separate, but the use of wireless protocols is not necessarily confined to the entertainment system. For example, wireless tyre pressure/temperature sensors are installed in many cars and can be read with SDR hardware[1]. It's not too much of a leap to assume that false readings could be injected.

[1] http://sandiego.toorcon.net/2013/10/07/dude-wheres-my-car-re...