I don't know about other brands, but Rand McNally's RV and truck GPS's have that feature, and sell all the equipment.
I don't know why anyone would do that, the RM, RV and truck units come with a 7" screen. Having two 7" screens on the dash is cluttered, but I can watch my GPS and rear camera at the same time. Can't do that with one screen and two functions.
2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert theConstitution. "Abraham Lincoln"