As far as I can tell it's a helper for taking point-and-shoot pictures in automatic modes... i.e. something like "if and only if there is motion when you're half-shuttering, use a faster shutter speed and higher ISO, otherwise try to minimize noise using lower ISO".
Maybe we could try to simulate this using a script... when half shuttering, the script would let the camera auto exposure and then launch md_detect_motion with a very short timeout and if motion was detected, override shutter speed and ISO. Either Shooting should be tied to a button (or half-shutter tied to the trashcan button and full shutter to half-shutter or whatever).
I fear this might be painfully slow, though...
