Not clear on what you're asking. Are you talking about a door sensor to tell if it is closed and to use with a security system? Then yes, you want one. You can't use the door lock status as a security indicator.
On my system, when the door shuts and the contact is closed, my OmniPro sends a lock command to the deadbolt to automatically relock it. If you use the relock function of the deadbolt, it will relock after x seconds, but that may happen while the door is still open.
