Don't buy cheap aftermarket head unit as the specifications will differ from what the shopkeepers quote. It'll not provide good display and sound quality. Camera result is poor too and it will not have any warranty. I purchased and installed it in my car but disappointed by it.
Now I'm using OEM Honda City windows navigation which i purchased for 30k from tracking world. Rear view camera, remote control and a stylus pen was included in the package. It has Bluetooth, SD card support, navigation card for offline maps and many more. It comes with three years warranty.