Dave,
There has been talk about this system were warning flags are going to be replaced by lights in the cars cockpit. There are some existing plans to use this lighting system alongside flag waving marshals, although I suspect this is just to perfect the system before finally phasing out flags all together.
The biggest problem before introducing such a system is ensuring every circuit around the world complies and is fitted with the correct equipment. The Malaysia circuit was the first track in the world to be equipped with electronic marshals' posts which flash coloured lights to the drivers instead of flags. The circuit is covered by 27 closed circuit television cameras via fibre optic cabling and includes on-line, real time tracking of race cars, Hi-tech stuff.
Its not just the tracks either, every other motorsport would need the system fitted to their cars before we would see the end of flag waving marshals and even then they would need a back up system in case of a 'system' failure.
I'm sure the day will come when the only requirement for marshals to be on the track will be to attend and clear up after racing incidents. I take my hat off to them, its a dangerous job and many of them do it for little or no money.
Hope this helps.