We put a camera out at one point, before we got our "real" security system up and running. Employees thought it was on, and didn't even realize it was not hooked up. Cut down on a lot of missing things. The office is always locked when I'm not there, and no one has the key, so they just assumed I could watch it anytime.
Also, isn't there an average number of sprays that one container will do? I don't have one yet, so I am not sure, but it seems like one company told me you can spray about 45 customers with one gallon? My numbers could be way off, and I apologize if they are. But, either way, whatever system you have, you should be able to find out average sprays per gallon, and kind of look at it that way. When you get your next gallon, compare how many paid visits you had compared to when you run out of
solution . That way you can see if you had less pay then what you should have.