Door pay could be really important down the road. The FARs haven't changed, operators abilty to monitor forward movement under own power has. It started with the 777 and the EMB-145. All new [certified] airplanes since have been installed with wheel speed sensors [that can be recorded via the AirInc 429 bus.] This is not NEW - my previous carrier tried to do this is in 2003/04 but we stopped them with door pay and protections of recorded data.