I would suggest that for some elderly people whilst they may seem compos mentis in most aspects of their daily life, they would react very badly if they knew there was a camera in their room, no matter how it was explained to them it for for their own good.

My ex MIL for example long before going into a care home, could not be dissuaded that she wasn't being watched through the television and I don't think my mother would have been any different when she got to the stage where she wouldn't have been able to effectively protest at bad treatment.

More of a reason for an independent judge to decide in such a case.

I don't think for one moment your concerns are unwarranted but I do wonder what sort of evidence would be needed as at that stage you would only have suspicions, many signs of abuse may only be apparent to someone who knew the person well, meaning little to others.