It wouldn't have to be anything fancy, would it? Maybe each runway could have some kind of beacon set to respond back with a ping IDing which runway the plane was sitting on? Or maybe something keyed to flash the number of the runway when a plane is sitting at the end of it waiting to take off, before the plane begins to move. Someplace a pilot could see out the cockpit window, even in the dark and/or in inclement weather.
I have seen the signs with arrows that are on the taxiways and runways; plus various light, that I always assumed meant something to the pilot, like a red light on a traffic signal means something to me.
They already have lighted signs telling them which runway is which, I thought someone wanted an automatic alarm which would go off if you were on the wrong runway. Bitching Betty maybe? "Abort, Abort You are on the wrong runway, abort, abort." Don't think that would go over too well.