I often wonder what ever happened to Richard Walker's Firefly approach lighting system - seemed like a good idea over 10 years ago.
For those who don't know what it was - a VASIS like system that was adjustable for azimuth and elevation (using a radio code) that would give you the flashing green (high) green (on appropriate approach angle), red (slightly below) and flashing red (too low), just like a runway VASIS / PAPI.