The 2nd monitor will show the map with all the dots.
But why do we need a modern 3d card for this 2d feature?
My suggestion is to draw the map with GDI or something in a 2nd window, which users can drag, resize, etc (only with 2nd monitor option on)
Currently im using my PDA with Sidewindow, so i can use it as a second monitor. It would be nice to have the minimap there, because the size of the PDA is just right for it.

I think a 2nd monitor for the map will help a lot of users, using your onboard videocard as minimap viewer for example.