Features in Graphics
digiKam from trunk (KDE4) : I'm happy to said than a new powerfull Search tool is available in digiKam : Searches over a map !
This tool use Marble widget from trunk with a patch from me to perform a rectangle selection on the canvas. The patch is available at this url:
When you make a selection, digiKam query the database to find all pictures which have been taken into this area.
There is a screenshot of this tool in action at this url:
Several improvments need to be done in marble to have a more suitable selection tool, but at least it work fine as well.