The house is concrete block, are the interior walls studded? Do you have baseboards? In this instance the best solution would be to pull your baseboards, remove the drywall/plaster behind the baseboards and run the Cat 6 through the walls to your camera mounting locations. You shouldn't run into...
You would connect it to the Normally Open(NO) and the Common. When the Camera output triggers it will switch the relay and cause the contact to close completing the circuit for the NO and opening the circuit for the NC.
To answer your other question, yes this is exactly what you need.