I noticed today on a list of features on another Radar Site (it hasn't been released yet)
They plan to show approximate distance to Aircraft from your own site. This appears a very simple idea, but could be very effective.
The aircraft that do not appear on the map, including military, will show you the distance they are away from you, indicating the ones that are in your own area. You will know which ones they are, if they fly directly overhead.
Is this something that AirNav could do, as I certainly would be very interested in this feature. Or is your development of Multilat far superior.