By chance have you seen any units that also provide back up camera functionality?
I'm looking for a back up camera for the wife's vehicle and would like to have it support a second rearview camera on the back on the trailer when pulling that. The trailer camera would be for far more than backing....I'd like to be able to see what is behind me while driving. Far too many folks have no concept of being able to see the rear view mirrors of the tow vehicle and insist on tailgating.
If I could get the above, while also having a downloadable dash cam, especially for less than $1k, I'd be happy as a clam at high tide.
Others have mounted one pointing to the rear for that purpose.
Beyond that you are talikg about a specialized unit with camera in one location and screen in another - Blue Tooth maybe.