The fundamental utility of the DRV-520 is like practically every other dashcam that you've seen. It constantly records video of everything that is happening in front of your car and it comes with additional features like collision avoidance and impact detection. It records all of this onto a removable 8GB SD card. No surprises there.
Where the DRV-N520 differs is that it is not meant to operate as a standalone device. Instead, it pairs with your KENWOOD DMX7704S double-DIN media receiver. That's the thing you'd use for playing music, getting turn-by-turn navigation, and managing your Bluetooth hands-free phone calls. By taking advantage of this bigger screen, it's much easier to adjust the settings on your dashcam, adjust the display duration and so on.
The KENWOOD DRV-N520 has an MSRP of $200.