With cost coming down faster, camera's are pretty much everywhere these days. As long as people are informed there is monitoring it's fine.
However, there are hidden cameras aka spy cameras appearing in places they shouldn't be and increasingly becoming problematic.
This .biz TLD is an exact match for the term hidden cameras, easy to remember and has a lot of potential in the security niche.
Great news! Domain HiddenCameras.biz has been registered in the past and previous domain owner(s) may have forgot to renew or dropped it.