I agree that the emissions dynos (as used her for state inspection) are a little creepy...they use wheel chocks on the non-powered wheels but that's it (no chains, etc.).....if the dyno bearings failed or suddenly changed resistance, it would be all over for anyone standing in front of the car. BTW, One of our family sedans is a new Impreza 2.5 RS (think WRX without the turbo). They won't be able to test it (when it becomes due) because of the full-time 4WD (but it still get the tailpipe sniffer).
Also: there's a federal govenment effort to replace local emissions testing with a universal test that would link to the car's ALDL (diagnotic) port. Modern cars already record any "violations" of the emissions system (and of course, modern cars already have a built emissions sniffer system to control the fuel injection, etc). This was part of the post-ODB II regulations. The plan is: Once a year, you go down to your local motor vehicle office, they plug you in and they can tell if you're been "naughty or nice". Frankly, this doesn't really bother me, as long as they leave the old cars alone.
Related emissions story: the Spridget was idling in my driveway a few summers ago (still wearing it's original Zenith carb). I knew it was running too rich or lean or something, but I couldn't get it to "adjust out". Downwind of the driveway, about 30 feet away is the (open) window to my living room. All of a sudden, I hear this beeping sound. The Spridget had set off the Carbon Monoxide Alarm in my living room!