There were a few old threads on this topic so hopefully ok to start a new one as I am sure things have changed in the last few years.
I am looking for double DIN head unit and I see there are
a) $160 From eBay with Camera, Bluetooth Radio and GPS
b) $200 from TradeMe with Camera, Bluetooth Radio and GPS
c) $500+ from the big brands
Are these cheap ones any good? They are not the Android versions which I am guessing are really slow. (I tried to use a gen 1 Nexus 7 tablet in the car and was just unusable)
The main thing is the start up time to reverse camera display and bluetooth connect.
I am not to worried about the navigation feature am intrigued as to how easy they are to update.