RAT 5, I have to believe that the autonomous car folks are not planning on anyone monitoring anything. There is simply no way to possibly train the masses...it'll have to work without monitoring. Not that I think it will work...
Had a CSD overheat on the way back up from Mexico in the trusty old MD80 a couple of weeks ago. There is no master caution or annunciation; one simply has to make a routine scan of the overhead. We descended to start the APU, disconnected the generator, and the temp cooled...so we continued in that configuration. The FO remarked that, "Not many guys would have caught that..." Seriously? Why not? How much of this has to do with a generation disconnected from the habits developed while operating any type of machinery? If you like running machinery, you like watching it work...on the other hand, if you came up through the ranks of the video game crowd, monitoring may not come as naturally as it once did.
At the first moment you think you are bored, it's time to look around. But when it gets busy, active monitoring is tough if you a) don't have good SOP compliance, and b) don't communicate your intentions ahead of time. Next, as the monitoring pilot, communicate clearly...phrases like "Did you see that?" or "That looks weird" are not the least bit useful.
That said, fatigue will neutralize monitoring before it neutralizes anything else. First, they kill the sentries...
I have often joked that pilots who read in the cockpit are safer than pilots who don't, simply because on a long segment, the guy who doesn't read is staring out across the horizon, a million miles away. The guy who does read is so scared he's going to get caught with his pants down that he checks the panel every 30 seconds...