Work place security camera spying

I live in Iowa and at the work place there are visible security camera’s because it is a quick service restaurant, so the camera’s are located in strategic places. How ever with the New GM in the Store she monitor’s or spies on the crew from her own house and has at least on 3 occasion’s called even on the grave yard shift talking with the Manger on duty and either has the manger write-up the employee for standing around or has the employee get on the phone and she tells them she is watching them. She has forced an employee to sign a write up that was not totally correct in saying if the employee did not sign it the employee would not work and get there hour’s. Several people have asked her why she is spying from home and the GM says “Because I can and I can not be there 24 hour’s a day”. All the employee’s and management are in fear to say anything because they might get written up, fired or not get any hour’s and be forced to leave to find a new job. I’m lost and confused in Iowa on what is lawful and not and have no idea who or what or even where I should go about this, please help.