I recently installed reverse camera to my X. I didn't want to drill any large holes on the car so instead I placed it on the license plate. I thought about placing it in the center of the rear roundel emblem but the placement on the license plate looked more discrete. Camera I'm using is Sony CCD rear-view that I purchased from EBAY.

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2004 X5 4.4i
2001 E46 M3
1995 E34 525i
2008 Acura MDX
1984 Maserati
2011 997 Turbo