Collision avoidance tech

I am interested in finding out what the current state of the art is
regarding automated VISUAL detection of mid-air collision threats.
"Active" tech to avoid collisons such as devices that signal other
devices with position, speed, heading, etc. work well, but require that
everyone have the same or similar installed in their aircraft and that
those devices are turned on and working correctly. Passive tech would
not depend on the other guy's tech at all. Machine vision and the
technologies that comprise it are advancing rapidly, getting cheaper.
Fast processing and sensitive, high resolution imaging are available and
relatively cheap. Software to resolve the perceived threats, Flarm
software, already exists. I just saw a TED video of a machine that could
track flying mosquitos and shoot them down with a laser (I want one of
those). So, why don't we have electronic eyeballs watching out for
traffic for us? Yes, I understand that it might take more than one to
cover the full sphere around the aircraft.

Some small amount of poking around on the net has yielded not too much
info. I am thinking that some of y'all technically astute types that
populate this group would know more.