Telephone Systems
Telephone systems today can be incorporated into your home much like they are used in a business environment. Aside from the basics like multiple phone lines, voice mail and whole-home paging, custom telephone systems can also help you monitor your home.
For example, distinctive rings can replace your current doorbell to let you know when someone arrives, and at which door. Then, by picking up any phone in your home, you can talk to your visitor and let them in, if you choose.
For added convenience and security, add discrete video cameras at each entrance and tie the live video into your home audio/video distribution system so that you can see your visitor in any room at the touch of a button.