Hi Martin
The rear camera was powered up by reversing lamp of the car.
And the image is the same, but as you know, the wireless is using 2.4GHz wireless signal to transfer image, so it will affected somehow by the other signals, so I suggest you to buy the wire one as they are the same price.
And the rearview camera on the option is universal type, it is not specialized on the Mazda CX-7 car. If you require specilized one, you need to tell us after you placed the order or before placing the order, so that we can check the price for you.
The universal one on this option is USD35.
Regards!
Andy
By
Seicane