Only way i can see it done right, is with the camera seperated from the NAV unit, kinda like a lukas lk-7300 but with a NAV unit in the seperate DVR.
Then you can leave your inexpensive camera in the car, and just bring the NAV/DVR unit with you when leaving the car.
But yes. The navigation marked must be under pressure, many car have navigation from the factory, and every one have a smart phone.
Google navigation dont Work that good with my HTC win8 phone for some reason, but it was good on my samsung android phone.
I have been thinking on modding my dashbord a Little and build a android tablet into the middle of my dashbord where there is a Little drawer with a lid.
I have NAV in my headunit, but it is a poor chinese model, and the NAV software isent that good in my eyes.
My phone sit on the driver side door, my Suzuki have a Little fixed window in front of the larger window witch can go up and Down, fits like a glowe - is 100% visible and i can touch the screen without letting go of the steeringwheel.