I am starting up a rpg/pvp server that is using a sort of graveyard spawn so the need for a compass that points to spawn is not needed. It would be awesome if in each city I could run a command that would set a waypoint for the compass. The compass would act as normal pointing toward the area but if you get too far from point A and become closer to point B, the compass will then switch to the new closest city.
We do something similar on my server using http://dev.bukkit.org/server-mods/radiobeacon/ . You just power an iron block and add iron fence to the top to increase the distance it is detected by a compass. You can also attach a sign to it to give a custom name. With the compass you can right click to pick a certain one to navigate to if several are in range. No commands are needed for either the tower builders or the compass users. We love it