I've been a private pilot since the late '70s, and for most of that time I've had this idea bouncing around in my mind.
First, some background: the output from a RADAR system at an airport usually doesn't get displayed directly on a screen; the raw image is cluttered with noise, reflections from stationary objects, etc. Instead, the data are fed into a computer system that cleans up the image, adds in labels for specific aircraft, all on top of a simplified map of the area. It's a rather nice system, and it's too bad the controllers are the only people who see it.
What I'm suggesting is that each RADAR-equipped control tower should have a bit of extra equipment attached to their computer system. Program the computer to encapsulate the results of each "sweep" (a full rotation of the antenna) into a data packet with a standard format, then send that packet through a modulator into a standard aircraft-band radio transmitter. Thus, every few seconds, a complete "picture" of the traffic situation around that airport would be broadcast to any receiver in the area. (This is all "off-the-shelf" technology; it should be very cheap.)
Complementing the transmitter on the ground are the receivers in the air. Any aircraft equipped with a radio receiver, demodulator and display unit could display for the pilot all the aircraft around the airport. Couple the system into the transponder, and the display could "know" which of the aircraft was itself, enabling an option to re-center the display on the aircraft, instead of the airport. Adding a running computation to warn of possible collisions would be a trivial enhancement.
The real point of this is to take some of the load off those tired, overworked and overstressed controllers. Especially at the major hubs: O'Hare, Los Angeles, Denver, Kennedy, et al, the difficulty and complexity of the job is nigh overwhelming. After all, they have to watch everybody, and they have to do it with utter perfection, or a few hundred innocent people fall out of the sky. The Repeater system lets pilots watch their own vicinity, spreading the work of collision-avoidance out over dozens of people.
I thought this was a good idea when I first had it, and I still do. I'm a little surprised that no one else has thought of it. So here it is: do you like it, or hate it? Or do you know of something in the works that's even better?