I'm suddenly worried for reasons that are a long story and would out me. But as the title says really, I'm worried they might be illegal. But is it ok because it's in my own home? Interested in how many others use them/ how common it is.
Whilst it may be legal to covertly film if there is reasonable suspicion that an offence is taking place, using that footage for anything other than confronting the offender is unwise I feel. The footage may be sufficient to force them to resign, or give you a reason to dismiss but it may be challenged in an employment tribunal and the outcome of that will depend on all the circumstances involved.
If your nanny has worked for less than 2 years, assuming you are in the UK you can simply dismiss them with notice (paid notice if you don't want them working their notice period).
If trust has broken down to the point that you feel a hidden camera is necessary, then I feel you should give them notice. If you did use a hidden camera and you didn't see anything untoward, would you still be happy having that nanny care for your children, or would there still be a doubt in your mind?
I wouldn't like to work with a nanny cam. Whilst I have nothing to hide, I would feel truly uncomfortable and not be myself. I would wonder where there were others! I wouldn't be able to get down on the floor and be silly with the children and have play fights. I wouldn't sing nursery rhymes or silly made up songs, which the children adore because I am tone deaf and could not hold a note in a bucket!! Thankfully the children don't care! Also thankfully, my bosses trust me implicitly so I hope they wouldn't have a camera.
If i found out that my employer was filming me with a nanny cam I would leave immediately and probably consider taking legal action. I would not work in an environment where I was filmed, it would make me feel very very uncomfortable and like the family did not trust or respect me.