Directed has one for the X5 as well, but theirs also has an IR transmitter for wireless headphones. The Vizualogic linked to does not have one in it, and I don't know if any other VZ models have that. But if you're looking for rear-seat use, you will want headphones, and you will want wireless, and all the RF headphones anyone can afford will suck sometimes due to RF interference, so IR is the method of choice for reliability and sound quality.

My store works with both of these brands so contact me if you have any questions: )