Erm? Is this deliberately vague so that people will suggest what they think you mean and then you say..."That's it!"?

If so...Is this meant to be some kind of GPS add on that does the vector mathmatics of subtracting A^ from B^ and then accounting for curvature of the Earth to output a distance and direction?

Or just a reminder of the definition of the phrase "as the crow flies"?

I would call this device a 'human'.
Input to 'human'= a decent atlas, a ruler, and an understanding of how map scales work.
Output from 'human'= fairly rapid deduction of shortest distance between two points. At worst some scribbling to be undertaken on napkin or convinient back of envelope .

This can be acheived in UK using the PAF (Postcode Address File) available (at great cost) from the Post Office. Each UK postcode (there are ~1.7 million) has an associated X- and Y- grid reference, so with a bit of Pythagoras the distances between any two addresses can be calculated. For non-crow distances, there are several products out there (MapInfo's Drive-Time springs to mind) which take account of annoying details like roads. I assume that all countries have their own equivalents of PAF; I know that USA, Canada and Australia have.

tw: try the great circle mapper (see link). you just enter the airport codes of the cities invovlved, and it gives you the distance between. i think you can also input co-ordinates of some kind, but i'm not sure. i'm a little new to it myself.

<after some browsing...> from the great circle mapper:

Is there a simple way to compute great circle distances?

Assuming Earth is a perfect sphere of radius 6371.2 km, convert longitude and latitude to radians (multiply by pi/180), then compute as follows:

Autoroute 2000 can do this to +/- 1km for most of Europe. I think it uses the WGS84 GEoid (same as for GPS) so it's pretty accurate. So I guess this is Baked.

Kewell - I'll leave this up long enough for anybody to take advantage of the links. My search apparently used wrong terminology. Thanks (Don't understand why such an idea would get a fishbone - jealousy, perhaps - yeah, that's it - jealous, jealous, jealous)