gphoto2 has an option to download photos from a connected camera as they are shot (if the camera supports this). The command to do this is something like

gphoto2 --quiet --capture-tethered --keep --filename "$dir/%Y%m%d-gphoto-%06n.%C" --filenumber $n

If you choose a directory within a Digikam album and have Digikam running while shooting, the photos will directly appear in this folder.

It would be nice if this was integrated into Digikam directly, maybe as an option in the import dialog. The settings for folder and file naming could be taken from there, and there could be an option to delete the photos immediately from the camera (default off).