Just an idea... What you could do is the following:
Put the camera's in a separate organisation
Set a low idle timeout on it in Organization > Settings
Use the Organization > Login Attempts information for accountability
You could even have separate admins per network in it for more detailed info.
The problem with this is still that to check whether someone logged in, you'd have to login with the organization wide account, which in turn means that admin could watch camera imagery while supposedly checking the login attempts.
Maybe someone else has a better idea. But definitely make a wish and get contact with your sales rep to get it in as a formal feature request.