The DJI system is the state of the art consumer unit basically. With the caddx unit it's especially small (to fit on smaller quads):

https://www.quadcopters.co.uk/dji-hd-digital-fpv/iflight-suc...

The silver box and the camera are the relevant parts, the connection to the other PCB is just to receive telemetry from the flight controller.

Edit: better link to the actual unit itself:

https://www.buildyourowndrone.co.uk/caddx-fpv-air-unit-micro...