I will be installing a Panasonic Strada 905 NAV/BT/IPOD/XM unit with the reverse camera option. The wire from the Strada head unit for the camera just needs +12v when in reverse. They recommend splicing into the +12v connection to the back up light. That way when you shift to reverse the backup lights and the camera are turned on. BTW, the wire in the Strada harness for this is long enough to reach from the dash past the rear bumper in a Chevy Suburban! I think it would wrap twice around a smart. I am giong to slpice into the backup light in the right hand side rear "cubby hole". There is an easy to remove cover there, and should be easy to snake wire under the carpet up to the dash. Expect I'll mount the camera under lip above the license plate as it is very small.
BTW, if anyone else is installing this unit and you want to be able watch DVD's without setting the parking brake, instead of connecting the DVD enable wire to the parking brake switch just splice it to the +12v power wire for the head unit. That way any time the key is on and Strada is on you can view a DVD. Remember, it's not legal to watch while driving

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- David -