BMW has an optional camera that does it. But, not available in the states. Perhaps you can contact a supplier in Europe?I would like the aftermarket camera to plug in directly to the idrive unit if possible.
Is this compatible with the 2009 335i?Here is a good tutorial to start...
# Camera - a Pioneer ND-BC20PA (http://www.sonicelectronix.com/item_9820_Pioneer+ND-BC20PA.html)
# Video Interface - a NavVideo NV_BMW356 (http://www.navvideo.com/navvideo-models-nv_bmw356.asp)