There was a tiny demo of Maplet 2 floating around which allowed you to create a bunch of zones, press V and it would highlight what zones can be seen from other zones. It didn't export, save, load or anything useful though.
This at the time was Marks grand plan for Maplet and a built in vis system into blitz3d.
This appears to have disappeared probably never to see the light of day again, unless it's floating around for Max 3D? Who knows!
Thanks god we have Noel who defines what is good and what is not. I still use Maplet. Probably the development of Maplet was frozen due to the lack of people recognizing its potential.
Some things should be fixed/added tho (mentioned them earlier).