Depending on the year of your ride, you might have an AUX input pre-wired behind the screen - all you need is cable from dealer, about $40-60, or build the cable yourself from the Radio Shack parts, about $5-10... That is if you have the AUX pre-wired...

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E53 X5 4.6iS
147K mi - Sold May 2013
Tireprints left in:
USA, Nicaragua, Costa Rica, Panama, Russia

E53 X5 4.8iS built 2005-10-17
66200 mi - June 2012
96000 mi - June 2013
112000 mi - June 2014
OEM fire extinguisher
OE first aid kit
OE tow hitch
OE TV module
OE aspheric mirror
K&N air filter
black/white badges
rear camera
4-channel video recorder

Here is the list of things I have done to the X