Ported everything over to the Raspberry Pi and it works great, check out the video: 

The only gotcha was that Raspbian ships with USB audio configured off, but after a small config tweak it worked just like on the PC.  Very happy to see there aren't any performance issues and it seems to handle processing in real time without issue on the 700mhz Pi.

Next step is to integrate the thermal printer to print violations, and switch to a small amplifier & speaker.  On the software side I need to look at tweaking PocketSphinx to get better keyword spotting accuracy.

If time allows I might even start thinking about trying to get everything into an enclosure that mimics the look of the movie prop.  Something made of cardboard covered in aluminum tape would probably be simple enough to capture the look of the prop.