I was in Hong Kong for a few weeks attending a family wedding and visiting friends and family. Upon arrival I saw something like a ticketing booth in the immigration area:
So I stuck my smart-card Hong Kong ID card in and viola, in-and-out of immigration area in less than 10 seconds... cool!
Here is more info on the system.
My boss told me after the trip that this is similar to the NEXUS program. One difference is that every resident of Hong Kong has or will have this ID card and the system is to designed to process a high number of travellers at a very short time.