Best nanny cam systems

So after an incident at the daycare we have used for almost 3 years for our oldest and only two months of our youngest being there where our youngest had bad unexplained bruises (police report file, hospital trip for all injuries documented and daycare is under investigation) we have decided to hire a nanny. Due to the incident at daycare I’m very nervous of people watching my children but I have to return to work. The nanny we hired to start in the next 30 days knows we are putting cameras up and will monitor them regularly but I’m not sure what the best system to buy for as a nanny cam. So would like some in put on systems other moms use or have used