Comment too complicated (Score 3, Insightful) 127
> So, I'm thinking either face-recognition or retinal scans...
Waayyyy too complicated and expensive and Charlie's Angels-ish. If all you're trying to do is identify which user performed which step, RFID is your friend. Have an RFID sensor integrated into the workstation, and require the user to "sign" their work with their badge before they can commit.
Look at people going to work every day using RFID badges. If you want something faster than logging in with A/D credentials (which would have been my first suggestion), swiping a badge is pretty much as fast as you're going to find.
Now, if people using each other's credentials is a concern, or security in general, then you're looking at using A/D credentials plus a badge ("something you know, and something you have"). I personally wouldn't go with biometrics until they've gotten cheaper and more foolproof. Maybe never.