I know this is an old thread, but I had to comment because I am a PCA and sometimes get assigned to be a sitter. At my hospital, the sitter takes over all care for the patient: vitals, bathing, turns, feeding, bathroom, everything. We are also NOT allowed to study or look at our phones. If the patient is watching TV we can watch it with them, but otherwise we are just watching the patient. A lot of the patients are confused and trying to climb out of bed...I have literally redirected patients for hours.
Sometimes patients will sleep, and then I will chart my vitals/care, and read their H&P or look up their condition on the WOW. According to my hospital that is probably toeing the line for what is acceptable, but I feel like it's a need-to-know situation. The main thing is ensuring the patient's safety, and if they are suicidal you are literally expected to never take your eyes off of them. Sometimes these patients will deteriorate quickly too, and you are expected to be alert to any small changes in their condition and report to the RN. And sometimes nothing happens. The last patient I was a sitter for slept all night, and I ended up pacing (quietly) around the room to stay awake!
My point is for anyone applying for this type of job, find out what your hospital's policy is before planning that you will be able to do homework and study all night, because not all hospitals will allow you such leeway.