Here's an idea to prove they're watching the videos...at intervals, you display a unique ID to each feed, that the monitor has to enter on a keyboard. The interval should vary, as should the position on the screen. But the UID should appear on everyones feed at the same time; this should prevent one person from monitoring more than one feed at a time. You could/should have every feed monitored by more than one person. The feds could be run slightly out of sync/delayed, but still with the ID displayed at the same actual time. Therefor is someone was distracted by having to enter the ID, and missed someone shoplifting, another person wouldn't be.
Make sure you fully understand how the system is intended to work. Its all well and good knowing the stack, but equally important is knowing what you're meant to develop or fix. Also make sure you know the processes.
This is one of those ideas that seems so obvious. The solution looks great and the interface is solid. By the way, I'm +1 on emillon's mailing list idea