That would certainly be useful for enhancing situational awareness, particularly for TCAS. I can imagine a floating red circle around a conflicting flight with

That would certainly be useful for enhancing situational awareness, particularly for TCAS. I can imagine a floating red circle around a conflicting flight with a line extending out in the direction of flight (which is rather difficult to judge by sight alone). Too much would be distracting, of course, but I can't see any reason why it couldn't be developed with as much care and testing as traditional avionics are.