Tailgate Open?

My father retired as a Ford Motor Company service representative for the old tractor division (now 92 years old). Needless to say I have been a ford owner and supporter my entire life. I pulled ford tractors competitively also. My idea which I feel is LONG overdue is a sensor on pickup truck tailgates notifying the driver if you left the gate down. When you have a tonneau or certain caps you can leave your tailgate down accidentally and drive away. Every truck owner  I know has done this occasionally! Rear back up sensors will pick it up if you back up first, but if not, they will not warn you the tailgate is down. Like the tailgate step sounds a bit silly, but as the step has turned out to be a huge success, I believe this would be embraced too. Of course it could be disabled thru the vehicle controls. Thanks
Randy Santucci