Base / Tripod Mount
The SD9's flash hot-shoe has a single X-sync contact and three electronic flash connectors for use with Sigma's own STTL flash units the EF-500 DG Super SA and EF-500 DG ST SA. There is also a PC Sync terminal adapter (ST-11) which can be used to trigger studio / external flash units.
Lens Mount / Dust Protector
The Dust Protector is a good idea, however Sigma's QC needs a close look, the camera we had for testing had a considerable amount of dust already on the sensor surface which took some time to remove (this of course should not be necessary at all). Time will tell how well this dust protector actually functions.
Supplied In the Box
Slightly surprisingly there are no batteries supplied with the SD9, this means you'll have to get two CR-123A's as well as a set of four AA's or two CR-V3's. There is also no Compact Flash card provided, although this is not unusual for a digital SLR.