is it possible to have a security camera be able to be viewed realtime on a screen?
This would not be possible on ROBLOX with just a Camera. I believe their may be something you can do that's like the reflection game (Unsure of name) yet I don't know how that was done. Video feed cannot be played in Roblox games, neither can in-game video feed. Although, you can make it so your camera will move to another place to view that section.
Again, displaying a real-time video on a part in ROBLOX cannot be done.