I don’t think the present system is 100% but it’s close enough.
The question is would the Tzibur be willing to pay more for everything to ensure a higher level of Shmira.
I would put in cameras at all points of the restaurant and have someone review the tapes regularly that could find a problem.
There many Frum employed in the field but not enough to get 100 % of the staff.
Again, would you pay more to have frum people.